Changed button class (#1939)

Corona-Warn-App/src/main/res/layout/contact_diary_onboarding_fragment.xml

@@ -211,7 +211,7 @@
 
         </ScrollView>
 
-        <Button
+        <android.widget.Button
             android:id="@+id/contact_diary_onboarding_next_button"
             style="@style/buttonPrimary"
             android:layout_width="@dimen/match_constraint"

Corona-Warn-App/src/main/res/layout/contact_diary_person_bottom_sheet_fragment.xml

@@ -63,7 +63,7 @@
 
         </com.google.android.material.textfield.TextInputLayout>
 
-        <Button
+        <android.widget.Button
             android:id="@+id/contact_diary_person_bottom_sheet_save_button"
             style="@style/buttonPrimary"
             android:layout_width="@dimen/match_constraint"