test: fix flaky test-http2-respond-file-error-pipe-offset

Fixes: #35881

PR-URL: #36305
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: Trott

test/parallel/parallel.status

@@ -5,8 +5,6 @@ prefix parallel
 # sample-test                        : PASS,FLAKY
 
 [true] # This section applies to all platforms
-# https://github.com/nodejs/node/issues/35881
-test-http2-respond-file-error-pipe-offset: PASS,FLAKY
 
 [$system==win32]
 # https://github.com/nodejs/node/issues/20750

test/parallel/test-http2-respond-file-error-pipe-offset.js

@@ -56,4 +56,11 @@ server.listen(0, () => {
   req.end();
 });
 
-fs.writeFile(pipeName, 'Hello, world!\n', common.mustSucceed());
+fs.writeFile(pipeName, 'Hello, world!\n', common.mustCall((err) => {
+  // It's possible for the reading end of the pipe to get the expected error
+  // and break everything down before we're finished, so allow `EPIPE` but
+  // no other errors.
+  if (err?.code !== 'EPIPE') {
+    assert.ifError(err);
+  }
+}));