Update the comment of TextFormat::Printer::RegisterMessagePrinter tha…

…t the method takes ownerhip of the `printer` pointer.

The implementation takes ownership of the `printer`. But, the current method signature does not make it clear whether ownership is taken. In fact, since it's a `const *`, it could be easily confused by the callers as _not_ taking ownership.

All other `Register...Printer()` methods have comments about taking ownership. This is the only one that was left out.

PiperOrigin-RevId: 652584898

src/google/protobuf/text_format.h

@@ -440,6 +440,7 @@ class PROTOBUF_EXPORT TextFormat {
     // particular Descriptor.
     // Returns "true" if the registration succeeded, or "false" if there is
     // already a printer for that Descriptor.
+    // Takes ownership of the printer on successful registration.
     bool RegisterMessagePrinter(const Descriptor* descriptor,
                                 const MessagePrinter* printer);