Cleanup obsolete comment

Change-Id: Ic6706ee6c39cb54ad2f746f05e80fbc6a0af88e0

av1/common/entropy.c

diff --git a/av1/common/entropy.c b/av1/common/entropy.c
index 727ca09..ac9e8e7 100644
--- a/av1/common/entropy.c
+++ b/av1/common/entropy.c
@@ -752,9 +752,6 @@
   AVERAGE_TILE_CDFS(uni_comp_ref_cdf)
   AVERAGE_TILE_CDFS(comp_ref_type_cdf)
 #endif
-
-  // FIXME: cdfs not defined for super_tx
-
   AVERAGE_TILE_CDFS(inter_compound_mode_cdf)
 
   AVERAGE_TILE_CDFS(compound_type_cdf)