Update firebase-messaging version to 21.0.1 (#1884)
Update firebase-messaging version to 21.0.1 (#1884)

Co-authored-by: Dmitry Brant <8475e3dec5ba18bb5016c01b67ac232315694532@wikimedia.org>
Co-authored-by: Sharvani Haran <2228824a4af842f64fe485e276ab723cd575b489@users.noreply.github.com>
dbrant/apps-android-wikipedia,dbrant/apps-android-wikipedia,wikimedia/apps-android-wikipedia,wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia,wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia,wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia