Fix a -Wimplicit-fallthrough warning

Author: dr-m

storage/maria/ma_loghandler.c

@@ -6367,7 +6367,6 @@ my_bool translog_write_record(LSN *lsn,
  short_trid, &parts, trn, hook_arg);
  break;
  case LOGRECTYPE_NOT_ALLOWED:
- DBUG_ASSERT(0);
  default:
  DBUG_ASSERT(0);
  rc= 1;