Revert "Disable flaky ContentFaviconDriverTest.ShouldNotRequestRepeatedlyIfUnavailable"

This reverts commit 51bbb9a8.

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

Original change's description:
> Disable flaky ContentFaviconDriverTest.ShouldNotRequestRepeatedlyIfUnavailable
> 
> TBR=mastiz@chromium.org
> 
> Bug: 1011196
> Change-Id: Icd3cfd3860068b1530d5393868fedd2b6bcb2c78
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1839312
> 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@{#702699}

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

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

Bug: 1011196
Change-Id: I077f0d59b6cdb16694b06c517a950e2e45357f78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1853144Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704651}

components/favicon/content/content_favicon_driver_unittest.cc

@@ -120,8 +120,7 @@ TEST_F(ContentFaviconDriverTest, DISABLED_ShouldNotCauseImageDownload) {
 
 // Test that Favicon is not requested repeatedly during the same session if
 // the favicon is known to be unavailable (e.g. due to HTTP 404 status).
-TEST_F(ContentFaviconDriverTest,
-       DISABLED_ShouldNotRequestRepeatedlyIfUnavailable) {
+TEST_F(ContentFaviconDriverTest, ShouldNotRequestRepeatedlyIfUnavailable) {
   ON_CALL(favicon_service_, WasUnableToDownloadFavicon(kIconURL))
       .WillByDefault(Return(true));
   // Mimic a page load.