Disable UpdateMetricsProviderBrowserTest.RunInBackground on all platforms (#35399)

Disable UpdateMetricsProviderBrowserTest.RunInBackground in cross-platform filter

Move the test from browser_tests-windows.filter to browser_tests.filter so it
is disabled on all platforms (Linux, macOS, Windows). The upstream flake affects
any platform where a previous test subprocess exits uncleanly.

Resolves brave/brave-browser#54247

test/filters/browser_tests-windows.filter

@@ -72,7 +72,6 @@
 -PersistentBackground/ExtensionWebRequestApiTestWithContextType.WebRequestRedirectsWorkers/BackgroundResourceFetchEnabled
 -ServiceWorker/ExtensionWebRequestApiTestWithContextType.WebRequestRedirectsWorkers/BackgroundResourceFetchDisabled
 -ServiceWorker/ExtensionWebRequestApiTestWithContextType.WebRequestRedirectsWorkers/BackgroundResourceFetchEnabled
--UpdateMetricsProviderBrowserTest.RunInBackground
 
 # This test fails because we modify the Profile Picker UI to skip the initial
 # screen and the tests ends up creating 2 profiles instead of the intended one.

test/filters/browser_tests.filter

@@ -3608,3 +3608,10 @@
 # Not disabled by Chromium. No Brave chromium_src modifications in this area.
 # https://github.com/brave/brave-browser/issues/54104
 -SensitivePaymentRedactionMultiSourcePageContextFetcherBrowserTest.BasicRedactionInIframe
+
+# Chromium test: upstream flake. The globally registered UpdateMetricsProvider
+# may record histogram samples during browser startup (e.g. via initial
+# stability log). The test's histogram_tester_ starts at construction before
+# startup, so it captures stray samples and ExpectUniqueSample fails.
+# https://github.com/brave/brave-browser/issues/54247
+-UpdateMetricsProviderBrowserTest.RunInBackground