[JENKINS-43507] Fix tests

src/main/java/jenkins/plugins/git/GitSCMSource.java

@@ -174,7 +174,7 @@ public GitSCMSource(String id, String remote, String credentialsId, String remot
         this.remote = remote;
         this.credentialsId = credentialsId;
         List<SCMSourceTrait> traits = new ArrayList<>();
-        this.traits.add(new BranchDiscoveryTrait());
+        traits.add(new BranchDiscoveryTrait());
         if (!DEFAULT_INCLUDES.equals(includes) || !DEFAULT_EXCLUDES.equals(excludes)) {
             traits.add(new WildcardSCMHeadFilterTrait(includes, excludes));
         }