Remove unnecessary macros

Change-Id: Id0975947b4e7b76b2c2464905f3b9a29245946c2

vp10/encoder/encoder.c

@@ -3384,8 +3384,6 @@ void vp10_update_reference_frames(VP10_COMP *cpi) {
   BufferPool *const pool = cm->buffer_pool;
   const int use_upsampled_ref = cpi->sf.use_upsampled_references;
   int new_uidx = 0;
-#if CONFIG_EXT_REFS
-#endif  // CONFIG_EXT_REFS
 
   // NOTE: Save the new show frame buffer index for --test-code=warn, i.e.,
   //       for the purpose to verify no mismatch between encoder and decoder.