Mark the API of Settings.getDefaultAccount and

Settings.setDefaultAccount as deprecated.

Bug: 352313110
Test: local test
Flag: android.provider.new_default_account_api_enabled

	modified:   core/java/android/provider/ContactsContract.java
        modified:   core/api/current.txt
        modified:   core/api/system-current.txt

Change-Id: I61b37969c2e7a7083e72f3f3ee69b7926d63501a