chore(deps): update actions/checkout action to v6 (#303)

Reviewed-on: https://gitea.com/gitea/docs/pulls/303
Co-authored-by: Renovate Bot <renovate-bot@gitea.com>
Co-committed-by: Renovate Bot <renovate-bot@gitea.com>

.gitea/workflows/build-and-publish.yaml

@@ -10,7 +10,7 @@ jobs:
   build-docs:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 20

.gitea/workflows/test.yaml

@@ -7,7 +7,7 @@ jobs:
   build-docs:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 20

.gitea/workflows/update_swagger.yaml

@@ -9,7 +9,7 @@ jobs:
   update-swagger:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - run: |
           wget https://raw.githubusercontent.com/go-gitea/gitea/refs/heads/main/templates/swagger/v1_json.tmpl
           sed -i "$@" 's\"version": "{{AppVer | JSEscape}}"\"version": "dev"\' v1_json.tmpl