refactor(binding): key_binding_t 不再保存按键序列字符串指针

src/core/binding.c

@@ -175,7 +175,6 @@ bool binding_table_add_bind(
   if (!parse_key_sequence(key_sequence, &modifiers, &keysym)) return false;
 
   auto item       = array_push(mode->items, mode->count, mode->capacity);
-  item->key_str   = key_sequence;
   item->modifiers = modifiers;
   item->keysym    = keysym;
   item->action    = action;

src/core/binding.h

@@ -10,7 +10,6 @@
 typedef struct binding_table_t binding_table_t;
 
 typedef struct key_binding_t {
-  const char *key_str;
   modifier_mask_t modifiers;
   keysym_t keysym;
   zdwm_action_t action;