message: update-required-checks.sh: fix argument handling
diff: @@ -10,7 +10,7 @@ fi
  if [ "$#" -eq 1 ]; then
  # If we were passed an argument, use that as the SHA
  - GITHUB_SHA="$0"
  + GITHUB_SHA="$1"
  elif [ "$#" -gt 1 ]; then
  echo "Usage: $0 [SHA]"
  echo "Update the required checks based on the SHA, or main."
  