test: mark test-http-server-request-timeouts-mixed flaky on macOS

PR-URL: nodejs/node#43597
Refs: nodejs/node#43465
Reviewed-By: Paolo Insogna <[email protected]>
Reviewed-By: LiviaMedeiros <[email protected]>

Author: F3n67u

test/parallel/parallel.status

@@ -23,6 +23,8 @@ test-fs-rmdir-recursive: PASS, FLAKY
 test-domain-error-types: PASS,FLAKY
 
 [$system==macos]
+# https://github.com/nodejs/node/issues/43465
+test-http-server-request-timeouts-mixed: PASS,FLAKY
 
 [$arch==arm || $arch==arm64]
 # https://github.com/nodejs/node/pull/31178