Bug 1747519 - disable test_http3_perf.js on Linux_64_opt for frequent failures. r=intermittent-reviewers,necko-reviewers,jmaher,kershaw DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D135108

netwerk/test/unit/xpcshell.ini

@@ -440,7 +440,9 @@ skip-if =
   os == 'linux' && bits == 64 && !debug # Bug 1710277
 run-sequentially = http3server
 [test_http3_perf.js]
-skip-if = os == 'android'
+skip-if =
+  os == 'android'
+  os == 'linux' && bits == 64 && !debug # Bug 1747519
 run-sequentially = http3server
 [test_http3_prio.js]
 skip-if = os == 'android'