fix: classify merged gitlab MRs as MERGE_REQUEST_MERGED (CM-1298)

API ingestion was emitting MERGE_REQUEST_CLOSED for merge requests with a
merged_at timestamp, so MERGE_REQUEST_MERGED activities never landed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Joana Maia <jmaia@contractor.linuxfoundation.org>

Author: joanagmaia

services/libs/integrations/src/integrations/gitlab/processStream.ts

@@ -192,7 +192,7 @@ const handleMergeRequestsStream: GitlabStreamHandler = async (ctx, api, data) =>
           data: item.data,
           user,
         },
-        type: GitlabActivityType.MERGE_REQUEST_CLOSED,
+        type: GitlabActivityType.MERGE_REQUEST_MERGED,
         projectId: data.projectId,
         pathWithNamespace: data.pathWithNamespace,
       })