[Sheriff] Disable HintsFetcherClearFetchedHints on flaky platforms

It looks like this and a number of related tests had been failing and
were recently reenabled; after the reenable, this one specifically is
still flaking.

Bug: 1166906
Change-Id: I0aca084860ad37976fdc736b7a1e64ed62c0134d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2630829
Commit-Queue: David Van Cleve <davidvc@chromium.org>
Commit-Queue: Michael Crouse <mcrouse@chromium.org>
Auto-Submit: David Van Cleve <davidvc@chromium.org>
Reviewed-by: Michael Crouse <mcrouse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843830}

chrome/browser/optimization_guide/hints_fetcher_browsertest.cc

@@ -792,6 +792,15 @@ IN_PROC_BROWSER_TEST_F(
       1, 1);
 }
 
+// TODO(crbug.com/1166906):
+// HintsFetcherBrowserTest.HintsFetcherClearFetchedHints is flaky on Windows and
+// Linux.
+#if defined(OS_WIN) || defined(OS_LINUX)
+#define MAYBE_HintsFetcherClearFetchedHints \
+  DISABLED_HintsFetcherClearFetchedHints
+#else
+#define MAYBE_HintsFetcherClearFetchedHints HintsFetcherClearFetchedHints
+#endif  // defined(OS_WIN) || defined(OS_LINUX)
 IN_PROC_BROWSER_TEST_F(HintsFetcherBrowserTest, HintsFetcherClearFetchedHints) {
   const base::HistogramTester* histogram_tester = GetHistogramTester();
   GURL url = https_url();