CircleCI: Fix Debian grep compatibility

Signed-off-by: Ted Hess <thess@kitschensync.net>

.circleci/config.yml

@@ -39,7 +39,7 @@ jobs:
                fi
 
                subject="$(git show -s --format=%s $commit)"
-               if echo "$subject" | grep -q -e '^[0-9A-Za-z,/_-+]\+: ' -e '^Revert '; then
+               if echo "$subject" | grep -q -e '^[0-9A-Za-z,+/_-]\+: ' -e '^Revert '; then
                  echo_green "Commit subject line seems ok ($subject)"
                else
                  echo_red "Commit subject line MUST start with '<package name>: ' ($subject)"