[CI] Try to fix breaking on both workflow run

.gitea/workflows/build-docs.yml

@@ -9,6 +9,8 @@ jobs:
     steps:
       - name: Set up Git repository
         uses: actions/checkout@v6
+        with:
+          ref: ${{ gitea.head_ref }}
       - name: Sign into gitea registry
         uses: https://github.com/docker/login-action@v3
         with:

.gitea/workflows/build-helpers.yml

@@ -10,6 +10,8 @@ jobs:
     steps:
       - name: Set up Git repository
         uses: actions/checkout@v6
+        with:
+          ref: ${{ gitea.head_ref }}
       - name: Run build
         run: ./build.sh
       - name: Upload compiled helpers