ci: move publish onto checkout@v7 and setup-node@v7 (#2)

The runner already reports v4 of both as Node 20 and force-runs them on 24.
Matching moshcode's pins takes the warning away before the forced migration
becomes a hard failure, and there is no behaviour here that depends on the
older versions.

Author: ralyodio

.github/workflows/publish.yml

@@ -36,9 +36,9 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 15
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: 24
           registry-url: https://registry.npmjs.org