[Sheriff] Disable MultipleRulesetsIndexingTest.StaticRuleCountExceeded.

This cl disables MultipleRulesetsIndexingTest.StaticRuleCountExceeded
on debug builds since it times out frequently.

Example build:
https://ci.chromium.org/p/chromium/builders/ci/Mac10.13%20Tests%20%28dbg%29/17957

TBR: karandeepb@chromium.org
Change-Id: I05a9b3e69f66694ac9627ab16383d480912433e1
Bug: 1071403
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2154600
Commit-Queue: Sahel Sharify <sahel@chromium.org>
Reviewed-by: Sahel Sharify <sahel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760087}

chrome/browser/extensions/api/declarative_net_request/declarative_net_request_unittest.cc

@@ -914,8 +914,8 @@ TEST_P(MultipleRulesetsTest, EnabledRulesCount) {
 
 // Ensure that exceeding the rules count limit across rulesets raises an install
 // warning.
-// Fails on Linux. See https://crbug.com/1071403
-#if defined(OS_LINUX)
+// Fails on Linux and debug builds. See https://crbug.com/1071403
+#if defined(OS_LINUX) || defined(DEBUG)
 #define MAYBE_StaticRuleCountExceeded DISABLED_StaticRuleCountExceeded
 #else
 #define MAYBE_StaticRuleCountExceeded StaticRuleCountExceeded