gha: update to actions/github-script@v7

- full diff: actions/github-script@v6.4.1...v7.0.1

breaking changes: https://github.com/actions/github-script?tab=readme-ov-file#v7

> Version 7 of this action updated the runtime to Node 20
> https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-javascript-actions
>
> All scripts are now run with Node 20 instead of Node 16 and are affected
> by any breaking changes between Node 16 and 20
>
> The previews input now only applies to GraphQL API calls as REST API previews
> are no longer necessary
> https://github.blog/changelog/2021-10-14-rest-api-preview-promotions/.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/.dco.yml

@@ -20,14 +20,14 @@ jobs:
           fetch-depth: 0
       -
         name: Dump context
-        uses: actions/github-script@v6
+        uses: actions/github-script@v7
         with:
           script: |
             console.log(JSON.stringify(context, null, 2));
       -
         name: Get base ref
         id: base-ref
-        uses: actions/github-script@v6
+        uses: actions/github-script@v7
         with:
           result-encoding: string
           script: |

.github/workflows/.test-prepare.yml

@@ -22,7 +22,7 @@ jobs:
       -
         name: Create matrix
         id: set
-        uses: actions/github-script@v6
+        uses: actions/github-script@v7
         with:
           script: |
             let matrix = ['graphdriver'];