reflect/protoreflect: use [] syntax to reference method

While godoc does not render comments within interface definitions,
using the [] syntax regardless helps with the replacement rules
we use to import Go Protobuf back into Google.

Change-Id: I0287ec3df5ba74261f563ce1117ab1e1be1fc270
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/635138
Reviewed-by: Cassondra Foesch <cfoesch@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/reflect/protoreflect/value.go b/reflect/protoreflect/value.go
index a7b0d06..a4b78ac 100644
--- a/reflect/protoreflect/value.go
+++ b/reflect/protoreflect/value.go
@@ -152,7 +152,7 @@
 	// This method may return nil.
 	//
 	// The returned methods type is identical to
-	// google.golang.org/protobuf/runtime/protoiface.Methods.
+	// [google.golang.org/protobuf/runtime/protoiface.Methods].
 	// Consult the protoiface package documentation for details.
 	ProtoMethods() *methods
 }