Remove `khash.h` leftovers.
MODIFY
include/mruby/proc.h
include/mruby/proc.h
@@ -133,7 +133,6 @@ MRB_API mrb_value mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx);
#include <mruby/khash.h>
-KHASH_DECLARE(mt, mrb_sym, mrb_method_t, TRUE)
MRB_API mrb_value mrb_load_proc(mrb_state *mrb, const struct RProc *proc);

MODIFY
mrbgems/mruby-symbol-ext/src/symbol.c
mrbgems/mruby-symbol-ext/src/symbol.c
#include <mruby.h>
-#include <mruby/khash.h>
#include <mruby/array.h>
#include <mruby/string.h>

Remove `khash.h` leftovers.