Use latest version truely compatible with macos 10.12

.gitlab-ci.yml

@@ -120,7 +120,7 @@ windows_test_python39:
     # Install pyopencl first to use a wheel from silx.org under Windows
     - pip install --find-links http://www.silx.org/pub/wheelhouse/ --trusted-host www.silx.org --prefer-binary pyopencl
     # Install latest compatible version of PyQt5 with macos 10.12
-    - pip install pyqt5==5.15.0
+    - pip install pyqt5==5.13.2
     - pip install --pre --find-links artifacts/ --only-binary silx silx[full,test]
     - python -c "import silx.test, sys; sys.exit(silx.test.run_tests());"