Codecov: don't annotate diffs

It makes it really annoying to read diffs when our coverage isn't that good yet.

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

.codecov.yml

@@ -16,6 +16,9 @@ comment:
   layout: "header, diff, changes, uncovered, tree"
   behavior: default
 
+github_checks:
+    annotations: false
+
 ignore:
   - "src/main/res/values*/*"