Install all requirements for pure python

.github/workflows/test_upb.yml

diff --git a/.github/workflows/test_upb.yml b/.github/workflows/test_upb.yml
index 42c0598..350dd10 100644
--- a/.github/workflows/test_upb.yml
+++ b/.github/workflows/test_upb.yml
@@ -299,8 +299,8 @@
           python -m venv env
           source env/bin/activate
           echo "VIRTUAL ENV:" $VIRTUAL_ENV
-      - name: Install numpy
-        run: pip install numpy
+      - name: Install requirements
+        run: pip install -r requirements/requirements.txt
       - name: Install Protobuf Wheels
         run: pip install -vvv --no-index --find-links wheels protobuf protobuftests
       - name: Run the unit tests