Raise required KSysGuard version to >=5.20.0
Required since commit 0fcecd6c.
With 5.19: src/page/FaceLoader.cpp:55:31: error: ‘class KSysGuard::SensorFaceController’ has no member named ‘setShouldSync’)
Required since commit 0fcecd6c.
With 5.19: src/page/FaceLoader.cpp:55:31: error: ‘class KSysGuard::SensorFaceController’ has no member named ‘setShouldSync’)