Remove duplicated entry for bwe_simulations.cc

Since modules_unittests already depends on
remote_bitrate_estimator:bwe_simulator and the bwe_simulations.cc
source was added to that target in https://codereview.webrtc.org/2296253002
there's no point having it added here.

BUG=webrtc:6323
NOTRY=True
NOPRESUBMIT=True
NOTREECHECKS=True

Review-Url: https://codereview.webrtc.org/2368933002
Cr-Commit-Position: refs/heads/master@{#14380}
diff --git a/webrtc/modules/BUILD.gn b/webrtc/modules/BUILD.gn
index 6f7f189..3aa1a7e 100644
--- a/webrtc/modules/BUILD.gn
+++ b/webrtc/modules/BUILD.gn
@@ -382,7 +382,6 @@
       "pacing/bitrate_prober_unittest.cc",
       "pacing/paced_sender_unittest.cc",
       "pacing/packet_router_unittest.cc",
-      "remote_bitrate_estimator/bwe_simulations.cc",
       "remote_bitrate_estimator/include/mock/mock_remote_bitrate_estimator.h",
       "remote_bitrate_estimator/include/mock/mock_remote_bitrate_observer.h",
       "remote_bitrate_estimator/inter_arrival_unittest.cc",