Temporarily disable grain synthesis

This is necessary due to this bug: https://bugs.chromium.org/p/aomedia/issues/detail?id=2768
I don't want to check every encoded video entirely just to make sure it doesn't contain this type of glitching.
Revert this commit once the issue is resolved in the aomenc.

hav1w.py

@@ -79,6 +79,8 @@ aom_params += ["enable-qm=1"]
 #
 # If you need to do grain synthesis on animation content, maybe SVT-AV1 is a better choice?
 # And read this: https://www.reddit.com/r/AV1/comments/n4si96/encoder_tuning_part_3_av1_grain_synthesis_how_it/
+# TEMPORARILY DISABLED DUE TO https://bugs.chromium.org/p/aomedia/issues/detail?id=2768
+preset["dnl"] = "-1"
 if preset["dnl"] != "-1":
     aom_params += ["enable-dnl-denoising=0", "denoise-noise-level=" + preset["dnl"]]