Remove bash conditional that caused windows runs to fail.

.github/workflows/build.yml

@@ -27,7 +27,6 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install flake8 pytest
-        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names