Remove unused MRB_TT_FILE.

src/etc.c

@@ -132,7 +132,6 @@ mrb_obj_id(mrb_value obj)
   case MRB_TT_HASH:
   case MRB_TT_RANGE:
   case MRB_TT_EXCEPTION:
-  case MRB_TT_FILE:
   case MRB_TT_DATA:
   case MRB_TT_ISTRUCT:
   default:

src/object.c

@@ -366,7 +366,6 @@ static const struct types {
   {MRB_TT_STRING, "String"},
   {MRB_TT_RANGE,  "Range"},
 /*    {MRB_TT_BIGNUM,  "Bignum"}, */
-  {MRB_TT_FILE,   "File"},
   {MRB_TT_DATA,   "Data"},  /* internal use: wrapped C pointers */
 /*    {MRB_TT_VARMAP,  "Varmap"}, */ /* internal use: dynamic variables */
 /*    {MRB_TT_NODE,  "Node"}, */ /* internal use: syntax tree node */