Remove outdated comments from descriptor.proto

The `retention` and `target` options have been functional for a long time, so
we can delete these stale comments saying that they do not work yet.

PiperOrigin-RevId: 673401292

src/google/protobuf/descriptor.proto

@@ -732,8 +732,6 @@ message FieldOptions {
   optional bool debug_redact = 16 [default = false];
 
   // If set to RETENTION_SOURCE, the option will be omitted from the binary.
-  // Note: as of January 2023, support for this is in progress and does not yet
-  // have an effect (b/264593489).
   enum OptionRetention {
     RETENTION_UNKNOWN = 0;
     RETENTION_RUNTIME = 1;
@@ -744,8 +742,7 @@ message FieldOptions {
 
   // This indicates the types of entities that the field may apply to when used
   // as an option. If it is unset, then the field may be freely used as an
-  // option on any kind of entity. Note: as of January 2023, support for this is
+  // option on any kind of entity.
-  // in progress and does not yet have an effect (b/264593489).
   enum OptionTargetType {
     TARGET_TYPE_UNKNOWN = 0;
     TARGET_TYPE_FILE = 1;