chore(deps): update actions/checkout action to v6 (#36)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/tex.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Set up Git repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Compile LaTeX document
         uses: xu-cheng/latex-action@v4
         with: