Revert "Disable flaky ContentFaviconDriverTest.ShouldNotCauseImageDownload"

This reverts commit 50d5253c.

Reason for revert: caused by crbug.com/1011275 which is now resolved.

Original change's description:
> Disable flaky ContentFaviconDriverTest.ShouldNotCauseImageDownload
> 
> TBR=mastiz@chromium.org
> 
> Bug: 1010207
> Change-Id: Ie1d8cea49b1aa5b1dfd785b1fe667e44fd96e7d0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1837317
> Reviewed-by: Yoichi Osato <yoichio@chromium.org>
> Commit-Queue: Yoichi Osato <yoichio@chromium.org>
> Auto-Submit: Yoichi Osato <yoichio@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#702318}

TBR=yoichio@chromium.org,mastiz@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1010207
Change-Id: I6ba594056c1fde18a8c7d62994f6f7d8f827f961
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1852987Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704652}

components/favicon/content/content_favicon_driver_unittest.cc

@@ -103,7 +103,7 @@ TEST_F(ContentFaviconDriverTest, ShouldCauseImageDownload) {
 
 // Test that no download is initiated when DocumentOnLoadCompletedInMainFrame()
 // is not triggered (e.g. user stopped an ongoing page load).
-TEST_F(ContentFaviconDriverTest, DISABLED_ShouldNotCauseImageDownload) {
+TEST_F(ContentFaviconDriverTest, ShouldNotCauseImageDownload) {
   ContentFaviconDriver* favicon_driver =
       ContentFaviconDriver::FromWebContents(web_contents());
   web_contents_tester()->NavigateAndCommit(kPageURL);