Bump actions/checkout from 3 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/lint.yml

@@ -10,7 +10,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           node-version: 26
@@ -19,7 +19,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v6
     - uses: actions/setup-node@v6
       with:
         node-version: 26

.github/workflows/test-gh.yml

@@ -26,8 +26,8 @@ jobs:
           - node:26-slim
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
         with:
           repository: nodejs/full-icu-test
           path: full-icu-test

.github/workflows/test-npm.yml

@@ -23,8 +23,8 @@ jobs:
           # Will fail on versions that aren't in icu4c-data
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
+      - uses: actions/checkout@v6
         with:
           repository: nodejs/full-icu-test
           path: full-icu-test