gitea latex workflow: full github path to latex action

.gitea/workflows/latex.yaml

@@ -7,7 +7,7 @@ jobs:
       - name: Set up Git repository
         uses: actions/checkout@v4
       - name: Compile LaTeX document
-        uses: xu-cheng/latex-action@v3
+        uses: https://github.com/xu-cheng/latex-action@v3
         with:
           root_file: Main.tex
           latexmk_shell_escape: true