Revert assert for debugging on CI

This reverts commit ac69849e49.
The bug seems to have been fixed.

vm_method.c

@@ -136,7 +136,6 @@ static void
 clear_method_cache_by_id_in_class(VALUE klass, ID mid)
 {
     VM_ASSERT(RB_TYPE_P(klass, T_CLASS) || RB_TYPE_P(klass, T_ICLASS));
-    if (!(RB_TYPE_P(klass, T_CLASS) || RB_TYPE_P(klass, T_ICLASS))) rb_bug("type confusion"); // temporary. Remove before release
 
     if (LIKELY(RCLASS_EXT(klass)->subclasses == NULL)) {
         // no subclasses