Revert "Introduce an empty WebRTC component."

This reverts commit 7777033e.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 707985 as the
culprit for failures in the build cycles as shown on:
https://analysis.chromium.org/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtLzc3NzcwMzNlZGFkMzA1ZTI5YThlMmM0OTk4ODIzNThkNzAxN2NhY2IM

Sample Failed Build: https://ci.chromium.org/b/8898950660954702496

Sample Failed Step: compile

Original change's description:
> Introduce an empty WebRTC component.
> 
> While testing the WebRTC component build in [1], there was a problem
> with some testonly code Chromium depends on (which cannot be part of the
> WebRTC component).
> 
> In order to support this use case, [2] will make the testonly code
> needed by Chromium depend on the WebRTC component and this CL is needed
> in order to land everything in an incremental fashion.
> 
> [1] - https://chromium-review.googlesource.com/c/chromium/src/+/1868961
> [2] - https://webrtc-review.googlesource.com/c/src/+/157427
> 
> Bug: webrtc:9419
> Change-Id: Ie995af67a7ab4ba1a2e5bb012f2e9b33be056acb
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872937
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#707985}


Change-Id: I259491613f592da9a5b4584de9fecca895d9398e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9419
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872944
Cr-Commit-Position: refs/heads/master@{#708016}

third_party/webrtc_overrides/BUILD.gn

@@ -10,10 +10,6 @@ group("webrtc_overrides") {
   ]
 }
 
-component("webrtc_component") {
-  public_deps = []
-}
-
 source_set("webrtc") {
   public_deps = [
     # TODO(kjellander): Start cleaning up this target as soon as