doc: Extend Gitaly /tmp workaround to cover Git execution path

Gitaly 14.7 until 14.9 have a bug where some files which are required at
runtime may be deleted by systemd-tmpfiles(1), which then renders the
instance broken. This bug affects two parts of Gitaly with Git hooks and
the Git execution path used for bundled Git.

We have recently documented a workaround for this bug by simply
disallowing the cleanup of these directories. This workaround only
applies to the hooks directory though, so it may still happen that the
Git execution environment is pruned. The consequence is that Gitaly
becomes unable to execute Git at all.

Fix this oversight by also excluding `/tmp/gitaly-git-exec-path-*` from
stale file cleanup.

doc/update/index.md

@@ -455,7 +455,7 @@ that may remain stuck permanently in a **pending** state.
   can override the behavior of `tmpfiles.d` for the Gitaly files and avoid this issue:
 
   ```shell
-  sudo echo "x /tmp/gitaly-hooks-*" > /etc/tmpfiles.d/gitaly-workaround.conf
+  sudo printf "x /tmp/gitaly-%s-*\n" hooks git-exec-path >/etc/tmpfiles.d/gitaly-workaround.conf
   ```
 
 ### 14.6.0