LoginForm: enable autocomplete on 2FA code field (#7019)

This should (fingers crossed) work in Safari, at least.

src/screens/Login/LoginForm.tsx

···
               autoCapitalize="none"
               autoFocus
               autoCorrect={false}
-              autoComplete="off"
+              autoComplete="one-time-code"
               returnKeyType="done"
               textContentType="username"
               blurOnSubmit={false} // prevents flickering due to onSubmitEditing going to next field