fix: add GROUPS to keyword rule for TestKeywordRuleCoverage

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

mdl/grammar/MDLParser.g4

@@ -3860,7 +3860,7 @@ keyword
 
     // Workflow
     | ABORT | ACTIVITY | ANNOTATION | BOUNDARY | BY | COMPLETE_TASK
-    | CONDITION | DATE | DECISION | DUE | INTERRUPTING | JUMP
+    | CONDITION | DATE | DECISION | DUE | GROUPS | INTERRUPTING | JUMP
     | LOCK | MULTI | NODE | NON | NOTIFICATION | NOTIFY
     | OPEN | OUTCOME | OUTCOMES | OVERVIEW | PARALLEL | PAUSE
     | REASON | RESTART | RETRY | SPLIT | TARGETING | TASK | TIMER