Disable flaky test DownloadTest#testDuplicateHttpPostDownload_Cancel

The test is flaky on multiple bots, see crbug.com/1130550.

BUG=1130550
NOTRY=true
TBR=xingliu@chromium.org,qinmin@chromium.org

Change-Id: If25b96affb01dd87458126cb01a848e9c2ff455c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421370Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808851}

chrome/android/javatests/src/org/chromium/chrome/browser/download/DownloadTest.java

@@ -260,6 +260,7 @@ import java.util.Set;
 
     @Test
     @MediumTest
+    @DisabledTest(message = "crbug.com/1130550")
     @Feature({"Downloads"})
     public void testDuplicateHttpPostDownload_Cancel() {
         // Remove download progress info bar.