fix merge handler tests with never rebuild feature

Signed-off-by: Brady Pratt <bpratt@redhat.com>

Author: jbpratt

src/test/java/com/dabsquared/gitlabjenkins/trigger/handler/merge/MergeRequestHookTriggerHandlerImplTest.java

@@ -368,7 +368,7 @@ public void mergeRequest_build_only_when_state_modified()throws IOException, Int
         MergeRequestHookTriggerHandler mergeRequestHookTriggerHandler = withConfig()
             .setTriggerOnAcceptedMergeRequest(true)
             .setTriggerOnClosedMergeRequest(true)
-            .setTriggerOpenMergeRequest(TriggerOpenMergeRequest.never)
+            .setTriggerOpenMergeRequest(TriggerOpenMergeRequest.source)
             .build();
         Git.init().setDirectory(tmp.getRoot()).call();
         tmp.newFile("test");