Update pip before we use it (#266)

apparently this is a thing

Author: Cadair

.github/workflows/publish_pure_python.yml

@@ -98,6 +98,7 @@ jobs:
       - id: set-env
         if: ${{ inputs.env != '' }}
         run: |
+          python -m pip install -U pip
           python -m pip install PyYAML
           echo $SET_ENV_SCRIPT | base64 --decode > set_env.py
           python set_env.py "${{ inputs.env }}"