Bump julia-actions/julia-downgrade-compat from 2.5.1 to 2.6.1 (#447)

Bumps [julia-actions/julia-downgrade-compat](https://github.com/julia-actions/julia-downgrade-compat) from 2.5.1 to 2.6.1.
- [Release notes](https://github.com/julia-actions/julia-downgrade-compat/releases)
- [Changelog](https://github.com/julia-actions/julia-downgrade-compat/blob/main/devdocs/release.md)
- [Commits](julia-actions/julia-downgrade-compat@f939b1a...fab1def)

---
updated-dependencies:
- dependency-name: julia-actions/julia-downgrade-compat
  dependency-version: 2.6.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/downgrade.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: julia-actions/setup-julia@fa02766e078afaaf09b14210362cee14137e6a32 # v3.0.2
         with:
           version: ${{ matrix.version }}
-      - uses: julia-actions/julia-downgrade-compat@f939b1ac65284d1440740bd15208dc61a07f65af # v2.5.1
+      - uses: julia-actions/julia-downgrade-compat@fab1defb76df9fd672f63c94df73ce131d32e134 # v2.6.1
         with:
           skip: Pkg,TOML,Mmap,Test,Random,InteractiveUtils
       - uses: julia-actions/julia-buildpkg@e3eb439fad4f9aba7da2667e7510e4a46ebc46e1 # v1.7.0