Disable codecov reports to GH comments.

erikjohnston · erikjohnston · commit 6be336c0d8b1 · 2019-07-31T10:56:02.000+01:00
The double posting is really annoying, and I don't think anyone is
actually reading them. The commit statuses should give a good summary
and will link to a full report.
diff --git a/.codecov.yml b/.codecov.yml
@@ -1,5 +1,4 @@
-comment:
-  layout: "diff"
+comment: off
 
 coverage:
   status:
