fix(datepicker): fix the DatepickerIOS align bug above 0.28.0 with the removing of width
fix(datepicker): fix the DatepickerIOS align bug above 0.28.0 with the removing of width

since 0.28.0, DatepickerIOS doesn't have specific width, extra code isn't need anymore.

can't be center automatic below 0.28.0. #13, #18

xgfe/react-native-datepicker,xgfe/react-native-datepicker,xgfe/react-native-datepicker