CI: avoid conflicts when rebasing the PR for linting

Prefer the changes that were accepted in main
over what is in the branch, as the conflict will
generally arise from an outdated base: the conflicting
changes are simply older versions of the file, and
replaying the whole history would eventually give
the same result.

Author: elegaanz

.github/workflows/test_pr.yml

@@ -68,7 +68,7 @@ jobs:
           git fetch origin ${{ github.base_ref }}
           git checkout ${{ github.base_ref }}
           git checkout $pr_head
-          git rebase ${{ github.base_ref }}
+          git rebase ${{ github.base_ref }} -X ours
       - uses: typst/[email protected]
         with:
           installation-id: ${{ secrets.GH_INSTALLATION_ID }}