Fix typo

@@ -111,7 +111,7 @@
             if (image && options & SDWebImageRefreshCached)
             {
                 // force progressive off if image already cached but forced refreshing
-                downloaderOptions ^= SDWebImageDownloaderProgressiveDownload;
+                downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload;
                 // ignore image read from NSURLCache if image if cached but force refreshing
                 downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse;
             }