ci: don't install dev dependencies

It conflicts with Cynthion's git dependency for now.

ci-scripts/build.sh

@@ -2,6 +2,6 @@
 set -e
 python3 -m venv testing-venv
 source testing-venv/bin/activate
-pip install .[dev]
+pip install .
 pip install "cynthion[gateware] @ git+https://github.com/greatscottgadgets/cynthion/#subdirectory=cynthion/python/"
 deactivate