Set only the ETS_TOOLKIT

Author: itziakos

.github/workflows/test-with-pip.yml

@@ -29,7 +29,6 @@ jobs:
     runs-on: ${{ matrix.os }}
     env:
       ETS_TOOLKIT: qt4.${{ matrix.kiva-backend }}
-      QT_API: ${{ matrix.toolkit }}
     steps:
       - name: Check out
         uses: actions/checkout@v4