Update Downgrade.yml

Author: ChrisRackauckas

.github/workflows/Downgrade.yml

@@ -30,6 +30,7 @@ jobs:
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
         with:
+          version: ${{ matrix.julia-version }}
           ALLOW_RERESOLVE: false
         env:
           GROUP: ${{ matrix.group }}