Merge pull request #44245 from thaJeztah/22.06_backport_api_update_swagger_for_builder_version

[22.06 backport] docs: swagger: update description for default builder version

docs/api/v1.42.yaml

@@ -8786,7 +8786,17 @@ paths:
               description: "Max API Version the server supports"
             Builder-Version:
               type: "string"
-              description: "Default version of docker image builder"
+              description: |
+                Default version of docker image builder
+
+                The default on Linux is version "2" (BuildKit), but the daemon
+                can be configured to recommend version "1" (classic Builder).
+                Windows does not yet support BuildKit for native Windows images,
+                and uses "1" (classic builder) as a default.
+
+                This value is a recommendation as advertised by the daemon, and
+                it is up to the client to choose which builder to use.
+              default: "2"
             Docker-Experimental:
               type: "boolean"
               description: "If the server is running with experimental mode enabled"