Set git credentials on the its-* plugins cross-branch builds

Run the generation of the .netrc credentials for the build
of its-* plugins on the cross-branch builds, which was initially
missed in the migration to the credentials-id of all jobs.

Change-Id: I9310c67e4ed734b114c49ae39e9c11d4d2934744
diff --git a/jenkins/gerrit-bazel-plugin-its-template.yaml b/jenkins/gerrit-bazel-plugin-its-template.yaml
index 88f62a0..c73cebc 100644
--- a/jenkins/gerrit-bazel-plugin-its-template.yaml
+++ b/jenkins/gerrit-bazel-plugin-its-template.yaml
@@ -76,6 +76,7 @@
           skip-tag: true
           do-not-fetch-tags: true
     builders:
+      - set-git-credentials
       - shell: !include-raw: gerrit-bazel-build-its-plugin-branch.sh
       - shell: !include-raw: gerrit-bazel-get-its-plugin-info.sh
     publishers: