Revert bumps in upstream-shared workflows to minimize merge conflicts

Keeps the 4vcpu host change in test.yml (already annotated with
# kilocode_change). The Node 20 deprecation warning stays for now;
`FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true` already forces the v4 actions to
Node 24 at runtime, so the warning is informational and CI still works.
Bumping all actions would require 40+ kilocode_change markers across
shared upstream workflows and invite conflicts on every upstream merge —
we'll pick up the version bumps when upstream does.

.github/workflows/check-opencode-annotations.yml

@@ -21,7 +21,7 @@ jobs:
     if: github.repository == 'Kilo-Org/kilocode'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v4
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           fetch-depth: 0