Disable flaky Chromium test SocketApiTest.SocketTCPExtension (#33980)

This is an upstream Chromium test with a 7.4% flake rate in LUCI
Analysis (30-day lookback, 78668 verdicts). Already disabled on
Windows by Chromium (crbug.com/1319604).

The test intermittently fails in testPendingCallback because the TCP
read returns only the HTTP headers without the body when the response
arrives in multiple TCP segments. Brave's chromium_src socket changes
(SOCKS5/SSL) are unrelated to the extension TCP socket API.

Resolves https://github.com/brave/brave-browser/issues/52872

test/filters/browser_tests.filter

@@ -3352,6 +3352,7 @@
 -SiteEngagementHelperBrowserTest.*
 -SitePerProcessWebViewTest.*
 -SmartSessionRestoreTest.CorrectLoadingOrder
+-SocketApiTest.SocketTCPExtension
 -SoundContentSettingObserverBrowserTest.*
 -SpeculationNoStatePrefetchBrowserTest.*
 -SpellcheckServiceBrowserTest.*