message: Remove GitHub Enterprise support notice on Firefox
diff: <hr>
  - <p class="no-firefox">
  + <p>
  If you're a GitHub Enterprise user, visit your Enterprise site, right-click on <a href="https://user-images.githubusercontent.com/1402241/32874388-e0c64150-cacc-11e7-9a50-eae3727fd3c2.png" target="_blank">Refined GitHub's icon in the toolbar</a> and select <strong>Enable Refined GitHub on this domain</strong>.
  </p>
  - <p class="only-firefox">
  - <a href="https://github.com/sindresorhus/refined-github/issues/840#issuecomment-349936195" target="_blank">GitHub Enterprise is not yet supported in Firefox</a>.
  - </p>
  </form>
  <script src="browser-polyfill.min.js"></script>
  <script src="options.js"></script>
  