change default to 1

Author: amerchDev

android/src/main/java/com/bluechilli/flutteruploader/FlutterUploaderInitializer.java

@@ -19,7 +19,7 @@
 public class FlutterUploaderInitializer extends ContentProvider {
 
   private static final String TAG = "UploaderInitializer";
-  private static final int DEFAULT_MAX_CONCURRENT_TASKS = 3;
+  private static final int DEFAULT_MAX_CONCURRENT_TASKS = 1;
   private static final int DEFAULT_UPLOAD_CONNECTION_TIMEOUT = 3600;
 
   @Override