Bump julia-actions/setup-julia from 1 to 2

Bumps [julia-actions/setup-julia](https://github.com/julia-actions/setup-julia) from 1 to 2.
- [Release notes](https://github.com/julia-actions/setup-julia/releases)
- [Changelog](https://github.com/julia-actions/setup-julia/blob/master/devdocs/making_a_new_release.md)
- [Commits](julia-actions/setup-julia@v1...v2)

---
updated-dependencies:
- dependency-name: julia-actions/setup-julia
  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/downgrade.yml

@@ -18,7 +18,7 @@ jobs:
         version: ['1.10']
     steps:
       - uses: actions/checkout@v5
-      - uses: julia-actions/setup-julia@v1
+      - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
       - uses: julia-actions/julia-downgrade-compat@v2