Bump actions/setup-python from 2 to 3

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 2 to 3.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v2...v3)

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

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

Author: dependabot[bot]

.github/workflows/release.yml

@@ -7,7 +7,7 @@ env:
   ARTIFACT_NAME: dist
   # The project's folder on Arduino's download server for uploading builds
   AWS_PLUGIN_TARGET: /tools/
-  # See: https://github.com/actions/setup-python/tree/v2#available-versions-of-python
+  # See: https://github.com/actions/setup-python/tree/v3#available-versions-of-python
   PYTHON_VERSION: "3.7"
   MCUBOOT_PATH: ${{ github.workspace }}/mcuboot
   IMGTOOL_PACKING_PATH: ${{ github.workspace }}/imgtool-packing
@@ -61,7 +61,7 @@ jobs:
         run: git apply -v "${{ env.IMGTOOL_PACKING_PATH }}/patches/"*
 
       - name: Set up Python ${{ env.PYTHON_VERSION }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version: ${{ env.PYTHON_VERSION }}
           architecture: ${{ matrix.python_arch }}