fix: .github: self.yml: Same branch checkout

Use switch to detach head, to avoid failure if current checkout branch
has the same name.

Signed-off-by: Jorge Marques <[email protected]>
(cherry picked from commit 424059e)

Author: gastmaier

.github/workflows.mirror/self.yml

@@ -15,9 +15,10 @@ jobs:
 
     - name: update-self
       run: |
+        git switch -d
         git fetch origin ${{ inputs.ci_branch }} --depth=1
         git fetch origin cron:cron -f
-        git checkout cron
+        git switch cron
         git rm .github/workflows -r
         git checkout origin/${{ inputs.ci_branch }} -- .github/workflows.mirror
         git mv .github/workflows.mirror .github/workflows