The "View on git.drupalcode.org" link is wrong

This does not seem to happen for Drupal 11 documentation pages, for example AccessAwareRouter: In that page, the View on git.drupalcode.org link is https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Routing%21AccessAwareRouter.php/class/AccessAwareRouter/11.x.
It still not the correct link, which should instead be https://git.drupalcode.org/project/drupal/-/blob/11.0.x/core/lib/Drupal/Core/Routing/AccessAwareRouter.php?ref_type=heads, for example, because the 11.x branch is the main branch, not a branch for the Drupal 11 release.

As a side note, I noticed that the View on git.drupalcode.org link is preceded by an icon, on Drupal 11 pages but not on Drupal 10 or Drupal 9 pages.

Basing on the code used by Formatter::getObjectGitUrl() and Branch::getSlug(), this is probably an issue caused by the slug value stored for each Drupal core branch.

The slug is only used for URL purposes. The title of the branch should be the same as the name of the branch, so the MR should do the trick.

Since the icon issue was also reported here, I'm providing a fix for it as well. We were overriding a variable and losing the previous value, where the styling library was loaded.

I've merged this and it will go in the next deployment.