Consistently install branch specific dependencies in CI (#25874)

.github/workflows/unit_test.yml

@@ -29,7 +29,9 @@ jobs:
     - uses: actions/checkout@v6
       with:
         submodules: recursive
+
     - name: Install dependencies
       run: pip3 install -r requirements-dev.txt
+
     - name: Run tests
       run: qmk test-c