Clean up visibility and dependencies of RTC event log build targets.

- Remove visibility of encoder target.
- Remove unnecessary dependency on task_queue.
- Remove CreateRtcEventLogFactory() declaration from the rtc_event_log_api target
  since the function is not defined in that target.

Bug: None
Change-Id: Id9edee86f358d08ea063d62bd96e9653c5b06d55
Reviewed-on: https://webrtc-review.googlesource.com/c/116060
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26215}

sdk/android/native_unittests/peerconnection/DEPS

@@ -1,4 +1,5 @@
 include_rules = [
+  "+logging/rtc_event_log/rtc_event_log_factory.h",
   "+media/base",
   "+media/engine",
   "+modules/audio_processing/include/audio_processing.h",

sdk/android/native_unittests/peerconnection/peerconnectionfactory_unittest.cc

@@ -12,6 +12,7 @@
 #include "absl/memory/memory.h"
 #include "api/audio_codecs/builtin_audio_decoder_factory.h"
 #include "api/audio_codecs/builtin_audio_encoder_factory.h"
+#include "logging/rtc_event_log/rtc_event_log_factory.h"
 #include "media/base/mediaengine.h"
 #include "media/engine/internaldecoderfactory.h"
 #include "media/engine/internalencoderfactory.h"