Remove need for synchronized access to ApiProvider instance

@WorkerThread

public class ApiProvider {

    private static ApiProvider instance;

    private static final String TAG = ApiProvider.class.getSimpleName();

    private static final ApiProvider INSTANCE = new ApiProvider();

    private static final String API_ENDPOINT_OCS = "/ocs/v2.php/cloud/";

    private final Map<String, NextcloudAPI> API_CACHE = new HashMap<>();

    private static final Map<String, NextcloudAPI> API_CACHE = new HashMap<>();

    private final Map<String, OcsAPI> API_CACHE_OCS = new HashMap<>();

    private final Map<String, NotesAPI> API_CACHE_NOTES = new HashMap<>();

    private static final Map<String, OcsAPI> API_CACHE_OCS = new HashMap<>();

    private static final Map<String, NotesAPI> API_CACHE_NOTES = new HashMap<>();

    public static synchronized ApiProvider getInstance() {

        if (instance == null) {

            instance = new ApiProvider();

        }

        return instance;

    public static ApiProvider getInstance() {

        return INSTANCE;

    }

    private ApiProvider() {