3749 [in_app_purchase] Fixed some minor spelling mistakes in README (cla: yes, p: in_app_purchase)

3750 [in_app_purchase] Fix error message when trying to consume purchase on iOS (cla: yes, p: in_app_purchase)

3751 Revert “[in_app_purchase] Fix error message when trying to consume purchase on iOS” (cla: yes, p: in_app_purchase)

3752 [in_app_purchase] Fix error message when trying to consume purchase on iOS (cla: yes, p: in_app_purchase)

3753 [in_app_purchase] Update instructions on setting up example App (cla: yes, p: in_app_purchase)

3754 [google_maps_flutter] Fix handling of non-nullable invokeMethod return types (cla: yes, p: google_maps_flutter)