DevOps: Fix the CD workflow

The conditional of the `validate-release-tag` job was never matched
since it contained a type on the organization using `circus-test`
instead of `circus-tent`. The `ubuntu` job also always installed Python
3.9 despite using a matrix of various versions.

.github/workflows/cd.yml

@@ -9,7 +9,7 @@ jobs:
 
     validate-release-tag:
 
-        if: github.repository == 'circus-test/circus'
+        if: github.repository == 'circus-tent/circus'
         runs-on: ubuntu-20.04
 
         steps:
@@ -48,7 +48,7 @@ jobs:
         -   name: Set up Python
             uses: actions/setup-python@v4
             with:
-                python-version: '3.9'
+                python-version: ${{ matrix.python-version }}
 
         -   name: Install system dependencies
             run: |