Update docker builder doc

docs/sources/use/builder.rst

@@ -107,8 +107,7 @@ The `ENV` instruction sets the environment variable `<key>` to the value
 functionally equivalent to prefixing the command with `<key>=<value>`
 
 .. note::
-    The environment variables are local to the Dockerfile, they will not persist
-    when a container is run from the resulting image.
+    The environment variables will persist when a container is run from the resulting image.
 
 2.7 INSERT
 ----------
@@ -122,6 +121,8 @@ curl was installed within the image.
 .. note::
     The path must include the file name.
 
+.. note::
+    This instruction has temporarily disabled
 
 3. Dockerfile Examples
 ======================
@@ -179,4 +180,4 @@ curl was installed within the image.
     # Will output something like ===> 695d7793cbe4
 
     # You'll now have two images, 907ad6c2736f with /bar, and 695d7793cbe4 with
-    # /oink.
+    # /oink.