test: remove unnecessary strictEqual() argument from remoteClose()

PR-URL: #20343
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/test-http-agent-keepalive.js

@@ -92,8 +92,7 @@ function remoteClose() {
         // waiting remote server close the socket
         setTimeout(common.mustCall(() => {
           assert.strictEqual(agent.sockets[name], undefined);
-          assert.strictEqual(agent.freeSockets[name], undefined,
-                             'freeSockets is not empty');
+          assert.strictEqual(agent.freeSockets[name], undefined);
           remoteError();
         }), common.platformTimeout(200));
       }));