Remove duplicate declarations

Also defined in include/ruby/internal/core/rarray.h which always
will be included.

internal/array.h

@@ -39,8 +39,6 @@ static inline void RARY_TRANSIENT_UNSET(VALUE ary);
 
 RUBY_SYMBOL_EXPORT_BEGIN
 /* array.c (export) */
-void rb_ary_detransient(VALUE a);
-void rb_ary_ptr_use_end(VALUE ary);
 RUBY_SYMBOL_EXPORT_END
 
 MJIT_SYMBOL_EXPORT_BEGIN