Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/release.yml

@@ -45,14 +45,14 @@ jobs:
 
     steps:
       - name: Checkout mcuboot repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           repository: mcu-tools/mcuboot
           path: ${{ env.MCUBOOT_PATH }}
           ref: v1.8.0 # the patches apply only to this version
 
       - name: Checkout imgtool-packing repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           path: ${{ env.IMGTOOL_PACKING_PATH }}
 
@@ -123,14 +123,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout mcuboot repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           repository: mcu-tools/mcuboot
           path: ${{ env.MCUBOOT_PATH }}
           ref: v1.8.0 # the patches apply only to this version
 
       - name: Checkout imgtool-packing repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           path: ${{ env.IMGTOOL_PACKING_PATH }}