test: set parallel http server test as flaky

Ref: #43465
PR-URL: #50227
Refs: #43465
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Vinícius Lourenço Claro Cardoso <[email protected]>
Reviewed-By: Marco Ippolito <[email protected]>
Reviewed-By: Filip Skokan <[email protected]>

Author: anonrig

test/parallel/parallel.status

@@ -26,6 +26,8 @@ test-worker-nearheaplimit-deadlock: PASS, FLAKY
 test-domain-error-types: PASS,FLAKY
 # https://github.com/nodejs/node/issues/47420
 test-file-write-stream4: PASS,FLAKY
+# https://github.com/nodejs/node/issues/43465
+test-http-server-request-timeouts-mixed: PASS, FLAKY
 
 [$system==linux || $system==win32]
 # https://github.com/nodejs/node/issues/49605