Broken master: Failing karma test

As seen in https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/269969202, karma seems to be failing in EE:

FAILED TESTS:
  DiffFile
    template
      ✖ should render component with file header, file content components
        Chrome
      Expected 5 to be greater than 5.
          at VueComponent.<anonymous> (webpack:///builds/gitlab-org/gitlab-ee/spec/javascripts/diffs/components/diff_file_spec.js:31:1 <- spec/javascripts/test_bundle.js:2050336:61)
          at Array.<anonymous> (webpack:///builds/gitlab-org/gitlab-ee/node_modules/vue/dist/vue.esm.js:1989:1 <- spec/javascripts/test_bundle.js:1979728:12)
          at flushCallbacks (webpack:///builds/gitlab-org/gitlab-ee/node_modules/vue/dist/vue.esm.js:1915:1 <- spec/javascripts/test_bundle.js:1979654:14)

I'm not sure why we're not seeing a failing pipeline on master in CE, but I can reproduce the issue on CE via:

yarn karma-start --filter-spec spec/javascripts/diffs/components/diff_file_spec.js

It seems the value is exactly 5, not greater than 5.

If I revert gitlab-org/gitlab-ce!30927, the problem goes away.

/cc: @sming-gitlab, @mikegreiling