test: Remove unnecessary assertion

It only fails once in about 1000 times, but that's too many.
It's timing dependent, and the main behavior is covered by the other
assertions in the test anyway.

test/simple/test-http-client-agent.js

@@ -53,7 +53,6 @@ function request(i) {
     socket.on('close', function() {
       ++count;
       if (count < max) {
-        assert.equal(http.globalAgent.sockets[name].length, max - count);
         assert.equal(http.globalAgent.sockets[name].indexOf(socket), -1);
       } else {
         assert(!http.globalAgent.sockets.hasOwnProperty(name));