Bump julia-actions/setup-julia from 2 to 3

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

---
updated-dependencies:
- dependency-name: julia-actions/setup-julia
  dependency-version: '3'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/Downgrade.yml

@@ -21,7 +21,7 @@ jobs:
         julia-version: ['1.10']
     steps:
       - uses: actions/checkout@v6
-      - uses: julia-actions/setup-julia@v2
+      - uses: julia-actions/setup-julia@v3
         with:
           version: ${{ matrix.julia-version }}
       - uses: julia-actions/julia-downgrade-compat@v2