delete duplicated function overload

The `using engine<...snip...>::define;` line already defines this
function.  We don't have to repeat.

include/ruby/backward/cxxanyargs.hpp

@@ -512,7 +512,6 @@ struct driver {
     template<bool b> struct specific< 0, b> : public engine< 0, VALUE(*)(VALUE)> {};
     template<bool b> struct specific<-1, b> : public engine<-1, VALUE(*)(int argc, VALUE *argv, VALUE self)> {
         using engine<-1, VALUE(*)(int argc, VALUE *argv, VALUE self)>::define;
-        static inline void define(VALUE c, T m, VALUE(*f)(int argc, VALUE *argv, VALUE self)) { F(c, m, reinterpret_cast<type *>(f), -1); }
         static inline void define(VALUE c, T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self)) { F(c, m, reinterpret_cast<type *>(f), -1); }
         static inline void define(VALUE c, T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self, VALUE)) { F(c, m, reinterpret_cast<type *>(f), -1); }
     };
@@ -558,7 +557,6 @@ struct driver0 {
     template<bool b> struct specific< 0, b> : public engine< 0, VALUE(*)(VALUE)> {};
     template<bool b> struct specific<-1, b> : public engine<-1, VALUE(*)(int argc, VALUE *argv, VALUE self)> {
         using engine<-1, VALUE(*)(int argc, VALUE *argv, VALUE self)>::define;
-        static inline void define(T m, VALUE(*f)(int argc, VALUE *argv, VALUE self)) { F(m, reinterpret_cast<type *>(f), -1); }
         static inline void define(T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self)) { F(m, reinterpret_cast<type *>(f), -1); }
         static inline void define(T m, VALUE(*f)(int argc, const VALUE *argv, VALUE self, VALUE)) { F(m, reinterpret_cast<type *>(f), -1); }
     };