api: Document `version` in `/build`

It was introduced in API v1.38 but wasn't documented.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

api/swagger.yaml

@@ -8331,6 +8331,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.38.yaml

@@ -6356,6 +6356,16 @@ paths:
           description: "Target build stage"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.39.yaml

@@ -7390,6 +7390,16 @@ paths:
           description: "Target build stage"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.40.yaml

@@ -7701,6 +7701,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.41.yaml

@@ -7906,6 +7906,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.42.yaml

@@ -8156,6 +8156,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.43.yaml

@@ -8174,6 +8174,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"

docs/api/v1.44.yaml

@@ -8327,6 +8327,16 @@ paths:
           description: "BuildKit output configuration"
           type: "string"
           default: ""
+        - name: "version"
+          in: "query"
+          type: "string"
+          default: "1"
+          enum: ["1", "2"]
+          description: |
+            Version of the builder backend to use.
+
+            - `1` is the first generation classic (deprecated) builder in the Docker daemon (default)
+            - `2` is [BuildKit](https://github.com/moby/buildkit)
       responses:
         200:
           description: "no error"