Bump spack/setup-spack from 2 to 3

Bumps [spack/setup-spack](https://github.com/spack/setup-spack) from 2 to 3.
- [Release notes](https://github.com/spack/setup-spack/releases)
- [Changelog](https://github.com/spack/setup-spack/blob/main/CHANGELOG.md)
- [Commits](spack/setup-spack@v2...v3)

---
updated-dependencies:
- dependency-name: spack/setup-spack
  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/build.yaml

@@ -17,7 +17,7 @@ jobs:
       uses: actions/checkout@v6
 
     - name: Setup Spack
-      uses: spack/setup-spack@v2
+      uses: spack/setup-spack@v3
 
     - name: Spack version
       run: spack debug report