Try using pre-installed pip

Author: thomasspriggs

.github/workflows/pull-request-checks.yaml

@@ -158,8 +158,6 @@ jobs:
           # user input
           DEBIAN_FRONTEND: noninteractive
         run: |
-          sudo add-apt-repository universe
-          sudo apt-get install -yq python-pip
           pip install unidiff
       - name: Check updated lines of code match clang-format-7 style
         env: