[ruby/json] [ruby/json] Run have_func with the header providing the declarations

ruby/json@95fb084027

ruby/json@9d080765cc

Author: nobu

ext/json/parser/extconf.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 require 'mkmf'
 
-have_func("rb_enc_interned_str", "ruby.h") # RUBY_VERSION >= 3.0
+have_func("rb_enc_interned_str", "ruby/encoding.h") # RUBY_VERSION >= 3.0
 have_func("rb_hash_new_capa", "ruby.h") # RUBY_VERSION >= 3.2
 have_func("rb_hash_bulk_insert", "ruby.h") # Missing on TruffleRuby
 have_func("rb_category_warn", "ruby.h") # Missing on TruffleRuby