Bump julia-actions/julia-downgrade-compat from 1 to 2

Bumps [julia-actions/julia-downgrade-compat](https://github.com/julia-actions/julia-downgrade-compat) from 1 to 2.
- [Release notes](https://github.com/julia-actions/julia-downgrade-compat/releases)
- [Commits](julia-actions/julia-downgrade-compat@v1...v2)

---
updated-dependencies:
- dependency-name: julia-actions/julia-downgrade-compat
  dependency-version: '2'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/CI.yml

@@ -31,7 +31,7 @@ jobs:
         with:
           version: ${{ matrix.version }}
           arch: ${{ matrix.arch }}
-      - uses: julia-actions/julia-downgrade-compat@v1
+      - uses: julia-actions/julia-downgrade-compat@v2
         if: ${{ matrix.version == '1.6' }}
         with:
           skip: Pkg, TOML