Revert "AGC2 RNN VAD: Recurrent Neural Network impl"

This reverts commit 2491cb73820fe82923b848dfcab6772b4b0addb0.

Reason for revert: broke internal build

Original change's description:
> AGC2 RNN VAD: Recurrent Neural Network impl
> 
> RNN implementation for the AGC2 VAD that includes a fully connected
> layer and a gated recurrent unit layer.
> 
> Bug: webrtc:9076
> Change-Id: Ibb8b0b4e9213f09eb9dbe118bbdc94d7e8e4f91b
> Reviewed-on: https://webrtc-review.googlesource.com/72060
> Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
> Reviewed-by: Alex Loiko <aleloi@webrtc.org>
> Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#23101}

TBR=phoglund@webrtc.org,alessiob@webrtc.org,aleloi@webrtc.org,ivoc@webrtc.org

Change-Id: Ic311c4b7d79094e959d3a2c4a53c398f34c954e2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9076
Reviewed-on: https://webrtc-review.googlesource.com/74200
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23103}

tools_webrtc/libs/generate_licenses.py

@@ -44,7 +44,6 @@ LIB_TO_LICENSES_DICT = {
     'openmax_dl': ['third_party/openmax_dl/LICENSE'],
     'opus': ['third_party/opus/src/COPYING'],
     'protobuf': ['third_party/protobuf/LICENSE'],
-    'rnnoise': ['third_party/rnnoise/COPYING'],
     'usrsctp': ['third_party/usrsctp/LICENSE'],
     'webrtc': ['LICENSE', 'LICENSE_THIRD_PARTY'],
     'zlib': ['third_party/zlib/LICENSE'],