Mute the warning when debug mode is on

tx_type will always greater or equal to DCT_DCT

Change-Id: If82a02621443b231a9bf30b47f5ad41975761f9a
diff --git a/av1/common/blockd.h b/av1/common/blockd.h
index b2465ea..1386ad7 100644
--- a/av1/common/blockd.h
+++ b/av1/common/blockd.h
@@ -1072,7 +1072,7 @@
       tx_type = intra_mode_to_tx_type_context[mbmi->uv_mode];
     }
   }
-  assert(tx_type >= DCT_DCT && tx_type < TX_TYPES);
+  assert(tx_type < TX_TYPES);
   if (!av1_ext_tx_used[tx_set_type][tx_type]) return DCT_DCT;
   return tx_type;
 #endif  // CONFIG_TXK_SEL