Revert "Enable using a custom NetEqFactory in simulations"

This reverts commit 2a11b2451a4068746fa0c55fa210efd4a15e4423.

Reason for revert: Causes b/147826709

Original change's description:
> Enable using a custom NetEqFactory in simulations
> 
> Bug: webrtc:11005
> Change-Id: I8a15f77953cbd3c29a75c7cfc77f926b138994b9
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/165580
> Commit-Queue: Ivo Creusen <ivoc@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#30286}

TBR=kwiberg@webrtc.org,ivoc@webrtc.org

Change-Id: I14a0bd6ad2a90f1686b8b1a78f18aea9325871fe
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:11005
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/166403
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Commit-Queue: Sandeep Siddhartha <sansid@google.com>
Cr-Commit-Position: refs/heads/master@{#30288}

modules/audio_coding/neteq/tools/neteq_rtpplay.cc

@@ -397,8 +397,7 @@ int main(int argc, char* argv[]) {
   }
 
   std::unique_ptr<webrtc::test::NetEqTest> test =
-      factory.InitializeTestFromFile(/*input_filename=*/args[1],
-                                     /*factory=*/nullptr, config);
+      factory.InitializeTestFromFile(/*input_filename=*/args[1], config);
   RTC_CHECK(test) << "ERROR: Unable to run test";
   test->Run();
   return 0;