make glucose_model_mixin_factory importable from model_mixins

Author: erikvw

edc_glucose/model_mixins/__init__.py

@@ -1,5 +1,5 @@
 from .fasting_model_mixin import FastingModelMixin, fasting_model_mixin_factory
 from .fbg_model_mixin import FbgModelMixin, fbg_model_mixin_factory
-from .glucose_model_mixin import GlucoseModelMixin
+from .glucose_model_mixin import GlucoseModelMixin, glucose_model_mixin_factory
 from .hba1c_model_mixin import Hba1cModelMixin
 from .ogtt_model_mixin import OgttModelMixin, ogtt_model_mixin_factory