update copyright to 2021

ring-android/app/src/main/AndroidManifest.xml

...in/java/cx/ring/about/AboutBottomSheetDialogFragment.java

...ndroid/app/src/main/java/cx/ring/about/AboutFragment.java

...c/main/java/cx/ring/account/AccountCreationModelImpl.java

...src/main/java/cx/ring/account/AccountEditionFragment.java

...rc/main/java/cx/ring/account/AccountEditionPresenter.java

...app/src/main/java/cx/ring/account/AccountEditionView.java

.../src/main/java/cx/ring/account/AccountWizardActivity.java

...pp/src/main/java/cx/ring/account/BackupAccountDialog.java

...p/src/main/java/cx/ring/account/ChangePasswordDialog.java

...rc/main/java/cx/ring/account/ConfirmRevocationDialog.java

...roid/app/src/main/java/cx/ring/account/DeviceAdapter.java

...ain/java/cx/ring/account/HomeAccountCreationFragment.java

...main/java/cx/ring/account/JamiAccountConnectFragment.java

...ain/java/cx/ring/account/JamiAccountCreationFragment.java

...ain/java/cx/ring/account/JamiAccountPasswordFragment.java

...main/java/cx/ring/account/JamiAccountSummaryFragment.java

...ain/java/cx/ring/account/JamiAccountUsernameFragment.java

...rc/main/java/cx/ring/account/JamiLinkAccountFragment.java

...java/cx/ring/account/JamiLinkAccountPasswordFragment.java