actions: Use node20 runner (#35262)

GitHub has deprecated the node16 runner in favor of node20.
https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/

Thus, we need to make some updates:
* Update our actions to use the node20 runner.
* Update workflows to use new versions of various actions:
  - actions/cache v3 → v4
  - actions/setup-node v3 → v4
  - actions/github-script v6 → v7
  - actions/setup-node v3 → v4
  - actions/stale v8 → v9
  - github/codeql-action v2 → v3
  - peter-evans/repository-dispatch v2 → v3
* Update references to the above in some docs.
* Remove a long-commented-out job in gardening.yml

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/7668809904

.github/workflows/autorelease.yml

@@ -12,7 +12,7 @@ jobs:
     name: Release
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Create release
         env:
           API_TOKEN_GITHUB: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/autotagger.yml

@@ -21,7 +21,7 @@ jobs:
             exit 1
           fi
 
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           # We want to potentially trigger "tag" events, but the default GITHUB_TOKEN
           # explicitly does not trigger events.

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [3.2.0-alpha] - unreleased
+## [4.0.0-alpha] - unreleased
 
 This is an alpha version! The changes listed here are not final.
 
@@ -14,6 +14,7 @@ This is an alpha version! The changes listed here are not final.
 
 ### Changed
 - Updated package dependencies.
+- Use the node20 runner instead of the deprecated node16 runner.
 
 ## [3.1.0] - 2023-07-06
 ### Added
@@ -85,7 +86,7 @@ This is an alpha version! The changes listed here are not final.
 
 - Initial release
 
-[3.2.0-alpha]: https://github.com/Automattic/action-required-review/compare/v3.1.0...v3.2.0-alpha
+[4.0.0-alpha]: https://github.com/Automattic/action-required-review/compare/v3.1.0...v4.0.0-alpha
 [3.1.0]: https://github.com/Automattic/action-required-review/compare/v3.0.2...v3.1.0
 [3.0.2]: https://github.com/Automattic/action-required-review/compare/v3.0.1...v3.0.2
 [3.0.1]: https://github.com/Automattic/action-required-review/compare/v3.0.0...v3.0.1

action.yml

@@ -37,5 +37,5 @@ inputs:
       your organization's teams (`read:org`).
     required: true
 runs:
-  using: node16
+  using: node20
   main: dist/index.js

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "required-review",
-	"version": "3.2.0-alpha",
+	"version": "4.0.0-alpha",
 	"description": "Check that a Pull Request has reviews from required teams.",
 	"main": "index.js",
 	"author": "Automattic",