CI builds: Checkout main branch in a robust way (readthedocs#9793)

Adds an -f switch to force resetting the branch in cases where Circle CI has created it

Author: benjaoming

.circleci/config.yml

@@ -42,7 +42,7 @@ jobs:
       - run: git submodule sync
       - run: git submodule update --init
       - run: git fetch origin main  # needed for comparisson in pre-commit
-      - run: git branch --track main origin/main  # needed for comparisson in pre-commit
+      - run: git branch -f --track main origin/main  # needed for comparisson in pre-commit
       - run: pip install --user 'tox<5'
       - run: tox -e pre-commit
       - run: tox -e migrations