go/types, types2: update documentation for GoVersion

Update the documentation for Config.GoVersion to reflect the changes
made for #61175.

Change-Id: I9f3fbcf8ee88e52d6a5e7cf80dad3d2fb5313893
Reviewed-on: https://go-review.googlesource.com/c/go/+/511096


TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

src/cmd/compile/internal/types2/api.go

@@ -110,11 +110,11 @@ type Config struct {
 	// type checker will initialize this field with a newly created context.
 	Context *Context
 
-	// GoVersion describes the accepted Go language version. The string
-	// must follow the format "go%d.%d" (e.g. "go1.12") or ist must be
-	// empty; an empty string disables Go language version checks.
-	// If the format is invalid, invoking the type checker will cause a
-	// panic.
+	// GoVersion describes the accepted Go language version. The string must
+	// start with a prefix of the form "go%d.%d" (e.g. "go1.20", "go1.21rc1", or
+	// "go1.21.0") or it must be empty; an empty string disables Go language
+	// version checks. If the format is invalid, invoking the type checker will
+	// result in an error.
 	GoVersion string
 
 	// If IgnoreFuncBodies is set, function bodies are not

src/go/types/api.go

@@ -114,11 +114,11 @@ type Config struct {
 	// type checker will initialize this field with a newly created context.
 	Context *Context
 
-	// GoVersion describes the accepted Go language version. The string
-	// must follow the format "go%d.%d" (e.g. "go1.12") or it must be
-	// empty; an empty string disables Go language version checks.
-	// If the format is invalid, invoking the type checker will cause a
-	// panic.
+	// GoVersion describes the accepted Go language version. The string must
+	// start with a prefix of the form "go%d.%d" (e.g. "go1.20", "go1.21rc1", or
+	// "go1.21.0") or it must be empty; an empty string disables Go language
+	// version checks. If the format is invalid, invoking the type checker will
+	// result in an error.
 	GoVersion string
 
 	// If IgnoreFuncBodies is set, function bodies are not