ci: move Lock Threads to dessant/lock-threads v6.0.2 (#30)

The pinned v4.0.0 rejects the job token: it validates github-token at
100 characters or fewer, and Actions tokens are now longer, so every
scheduled run fails with '"github-token" length must be less than or
equal to 100 characters long'.

v6.0.2 accepts them. The workflow now matches the one phishing already
runs: empty top-level permissions, issues/pull-requests write on the job
only, process-only issues and PRs (discussions write is no longer
granted), and a 10 minute timeout. Each repository keeps its schedule.

.github/workflows/lock.yml

@@ -5,19 +5,22 @@ on:
   schedule:
     - cron: '20 2/3 * * *'
 
-
-permissions:
-  issues: write
-  pull-requests: write
-  discussions: write
+permissions: {}
 
 jobs:
   lock:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      issues: write
+      pull-requests: write
+    env:
+      YARN_ENABLE_SCRIPTS: false
     steps:
-      - uses: dessant/lock-threads@v5
+      - uses: dessant/lock-threads@89ae32b08ed1a541efecbab17912962a5e38981c # v6.0.2
         with:
           github-token: ${{ github.token }}
+          process-only: 'issues, prs'
           issue-inactive-days: '7'
           issue-comment: >
             This thread has been automatically locked since there has not been