Cleanup

app/src/main/java/eu/faircode/email/Helper.java

@@ -247,7 +247,6 @@ public class Helper {
 
     private static ExecutorService sSerialExecutor = null;
     private static ExecutorService sParallelExecutor = null;
-    private static ExecutorService sSerialTaskExecutor = null;
     private static ExecutorService sMediaExecutor = null;
     private static ExecutorService sDownloadExecutor = null;
 
@@ -266,12 +265,6 @@ public class Helper {
         return sParallelExecutor;
     }
 
-    static ExecutorService getSerialTaskExecutor() {
-        if (sSerialTaskExecutor == null)
-            sSerialTaskExecutor = getBackgroundExecutor(1, "task");
-        return sSerialTaskExecutor;
-    }
-
     static ExecutorService getMediaTaskExecutor() {
         if (sMediaExecutor == null)
             sMediaExecutor = getBackgroundExecutor(0, 1, 3, "media");