Fix bash syntax error: missing closing quote in builds-mattermost.yaml

The line BODYLINE="${BODYLINE%\""}" was missing a closing double quote,
causing 'unexpected EOF while looking for matching quote' error.

Fixed to: BODYLINE="${BODYLINE%\""}"

Author: KrisSimon

.github/workflows/builds-mattermost.yaml

@@ -41,7 +41,7 @@ jobs:
           # Properly handle JSON-escaped body - strip outer quotes and truncate
           BODYLINE="$BODY"
           BODYLINE="${BODYLINE#\"}"
-          BODYLINE="${BODYLINE%\""}
+          BODYLINE="${BODYLINE%\"}"
           TRIMMED_BODY="${BODYLINE:0:350}"
 
           # Create JSON using jq for proper escaping