Merge pull request #4545 from shuujii/remove-unused-C-header-file-from-src-etc.c

Remove unused C header file from `src/etc.c`

src/etc.c

 /*
-** etc.c -
+** etc.c
 **
 ** See Copyright Notice in mruby.h
 */
@@ -8,8 +8,6 @@
 #include <mruby/string.h>
 #include <mruby/data.h>
 #include <mruby/class.h>
-#include <mruby/re.h>
-#include <mruby/irep.h>
 
 MRB_API struct RData*
 mrb_data_object_alloc(mrb_state *mrb, struct RClass *klass, void *ptr, const mrb_data_type *type)