Reenable SecureDNS captive portal test

Flakiness is expected to be resolved now that captive portal tests do
not make assumptions regarding GetLastActive() window.

Fixed: 11139282
Change-Id: Ic24aa19bfb6985188d8674763badcf8857bf1a5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611464Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840250}

chrome/browser/captive_portal/captive_portal_browsertest.cc

@@ -2866,9 +2866,7 @@ IN_PROC_BROWSER_TEST_F(CaptivePortalBrowserTest,
             GetInterstitialType(broken_tab_contents));
 }
 
-// Disabled due to flake. https://crbug.com/1113928
-IN_PROC_BROWSER_TEST_F(CaptivePortalBrowserTest,
-                       DISABLED_SecureDnsCaptivePortal) {
+IN_PROC_BROWSER_TEST_F(CaptivePortalBrowserTest, SecureDnsCaptivePortal) {
   PrefService* local_state = g_browser_process->local_state();
   local_state->SetString(prefs::kDnsOverHttpsMode,
                          SecureDnsConfig::kModeSecure);