test: remove message from strictEqual assertions

When an AssertionError happens, the value of headers['set-cookie']
is not reported. That information is useful for debugging.
Hence removed the value passed as the message in deepStrictEqual
assertions of test/parallel/test-http2-cookies.js

PR-URL: #20174
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

test/parallel/test-http2-cookies.js

@@ -48,8 +48,7 @@ server.on('listening', common.mustCall(() => {
 
   req.on('response', common.mustCall((headers) => {
     assert(Array.isArray(headers['set-cookie']));
-    assert.deepStrictEqual(headers['set-cookie'], setCookie,
-                           'set-cookie header does not match');
+    assert.deepStrictEqual(headers['set-cookie'], setCookie);
   }));
 
   req.on('end', common.mustCall(() => {