Fix stale version comment for actions/setup-node pin

PR #346 bumped the pinned SHA to the v7.0.0 tag but left the
trailing comment as "v6", which would mislead anyone auditing
the pin against its comment.

Author: BrentIO

.github/workflows/deploy-docs.yaml

@@ -34,7 +34,7 @@ jobs:
           aws-region: ${{ secrets.AWS_REGION }}
 
       - name: Setup Node.js
-        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v6
+        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7
         with:
           node-version: 24