[docs] Fix links in github user guide - graphite section

Mistakenly used markdown style rather than rst in #104499.

Author: mtrofin

llvm/docs/GitHub.rst

@@ -26,19 +26,19 @@ aren't associated with a pull-request **will be deleted**.
 Using Graphite for stacked Pull Requests
 ========================================
 
-[Graphite](https://app.graphite.dev/) is a stacked pull request tool supported
-by the LLVM repo (the other being [reviewable.io](https://reviewable.io)).
+`Graphite <https://app.graphite.dev/>`_ is a stacked pull request tool supported
+by the LLVM repo (the other being `reviewable.io <https://reviewable.io>`_).
 
-Graphite will want to create branches under `llvm/llvm-project` rather than your
+Graphite will want to create branches under ``llvm/llvm-project`` rather than your
 private fork, so the guidance above, about branch naming, is critical, otherwise
-`gt submit` (i.e. publish your PRs for review) will fail.
+``gt submit`` (i.e. publish your PRs for review) will fail.
 
-Use `gt config` then `Branch naming settings` and `Set a prefix for branch names`.
-Include the last `/`.
+Use ``gt config`` then ``Branch naming settings`` and ``Set a prefix for branch names``.
+Include the last ``/``.
 
 If you didn't do the above and Graphite created non-prefixed branches, a simple way to
-unblock is to rename (`git -m <old name> <new name>`), and then checkout the branch
-and `gt track`.
+unblock is to rename (``git -m <old name> <new name>``), and then checkout the branch
+and ``gt track``.
 
 Pull Requests
 =============