forgejo-ci: use default actions

.forgejo/workflows/preview.yaml

@@ -13,12 +13,12 @@ jobs:
           apk add git ikiwiki po4a perl-yaml-tiny tree nodejs jq coreutils curl
           echo "GITHUB_PR_NAME=$(curl -Ls ${{ github.server_url }}/api/v1/repos/${{ github.repository }}/pulls/${{ github.ref_name }} | jq .title | tr ' ' '-' | tr -d ':' | tr -d '"' | tr '[:upper:]' '[:lower:]' | tr '/' '-')" >> $GITHUB_ENV
       - name: Repo pull
-        uses: https://github.com/actions/checkout@v4
+        uses: actions/checkout@v4
         with:
           fetch-depth: 1
           token: ${{ secrets.PAGES_TOKEN }}
       - name: Public repo pull
-        uses: https://github.com/actions/checkout@v4
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: public