test: deflake http headers timeout keepalive

The second request in the headers-timeout test could finish its headers
before the next periodic timeout check ran. Leave it incomplete across
multiple checking intervals before sending the remaining headers.

Remove both macOS keepalive flaky expectations. c3aa86d already
extended the request-timeout test's margin to allow multiple checks.

Refs: #42741
Signed-off-by: Filip Skokan <panva.ip@gmail.com>
Assisted-by: Claude, Codex
PR-URL: #66320
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: panva

test/parallel/parallel.status

@@ -34,9 +34,6 @@ test-performance-function: PASS, FLAKY
 test-esm-loader-hooks-inspect-wait: PASS, FLAKY
 
 [$system==macos]
-# https://github.com/nodejs/node/issues/42741
-test-http-server-headers-timeout-keepalive: PASS,FLAKY
-test-http-server-request-timeout-keepalive: PASS,FLAKY
 # https://github.com/nodejs/node/issues/60050
 test-cluster-dgram-1: SKIP
 

test/parallel/test-http-server-headers-timeout-keepalive.js

@@ -70,7 +70,7 @@ server.listen(0, common.mustCall(() => {
         performRequestWithDelay(
           client,
           headersTimeout / 5,
-          headersTimeout,
+          headersTimeout * 2,
           true
         );
       }, defer).unref();