Update the comment for ctype to note that it's deprecated.

New code should prefer `features.(pb.cpp).string_type`. We can't use the `deprecated=true` option for now due to failing tests.

PiperOrigin-RevId: 643036543

src/google/protobuf/descriptor.proto

@@ -635,13 +635,14 @@ message MessageOptions {
 }
 
 message FieldOptions {
+  // NOTE: ctype is deprecated. Use `features.(pb.cpp).string_type` instead.
   // The ctype option instructs the C++ code generator to use a different
   // representation of the field than it normally would.  See the specific
   // options below.  This option is only implemented to support use of
   // [ctype=CORD] and [ctype=STRING] (the default) on non-repeated fields of
-  // type "bytes" in the open source release -- sorry, we'll try to include
-  // other types in a future version!
-  optional CType ctype = 1 [default = STRING];
+  // type "bytes" in the open source release.
+  // TODO: make ctype actually deprecated.
+  optional CType ctype = 1 [/*deprecated = true,*/ default = STRING];
   enum CType {
     // Default mode.
     STRING = 0;