test: simplify assertion in http2 tests

In test-http2-timeout-large-write.js and
test-http2-timeout-large-write-file.js:

Use assert.ok() on a boolean that the test itself creates and sets,
rather than assert.strictEqual(). This allows us to use a static message
without running afoul of the upcoming "do not use string literals with
assert.strictEqual()" lint rule.

Backport-PR-URL: #22912
PR-URL: #22849
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/sequential/test-http2-timeout-large-write-file.js

@@ -48,7 +48,7 @@ server.on('stream', common.mustCall((stream) => {
 }));
 server.setTimeout(serverTimeout);
 server.on('timeout', () => {
-  assert.strictEqual(didReceiveData, false, 'Should not timeout');
+  assert.ok(!didReceiveData, 'Should not timeout');
 });
 
 server.listen(0, common.mustCall(() => {

test/sequential/test-http2-timeout-large-write.js

@@ -40,13 +40,13 @@ server.on('stream', common.mustCall((stream) => {
   stream.write(content);
   stream.setTimeout(serverTimeout);
   stream.on('timeout', () => {
-    assert.strictEqual(didReceiveData, false, 'Should not timeout');
+    assert.ok(!didReceiveData, 'Should not timeout');
   });
   stream.end();
 }));
 server.setTimeout(serverTimeout);
 server.on('timeout', () => {
-  assert.strictEqual(didReceiveData, false, 'Should not timeout');
+  assert.ok(!didReceiveData, 'Should not timeout');
 });
 
 server.listen(0, common.mustCall(() => {