[Ruby] Fix deprecation warnings with Ruby 3.x

Fix deprecation warnings about ANYARGS when compiling  C++ code for
SWIG-generated Ruby wrappers with Ruby 3.x.

This is a recurrence of a problem fixed in 4.0.2.  Our fix was
conditional on RB_METHOD_DEFINITION_DECL being defined, but Ruby
3.0 stopped defining this.
2 files changed