[Cleanup] Add missing #include. Remove useless ones. IWYU part 2.

This is a follow-up to
https://webrtc-review.googlesource.com/c/src/+/106280.
This time the whole code base is covered.
Some files may have not been fixed though, whenever the IWYU tool
was breaking the build.

Bug: webrtc:8311
Change-Id: I2c31f552a87e887d33931d46e87b6208b1e483ef
Reviewed-on: https://webrtc-review.googlesource.com/c/111965
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25830}
diff --git a/pc/localaudiosource_unittest.cc b/pc/localaudiosource_unittest.cc
index fe3a0e2..d28014a 100644
--- a/pc/localaudiosource_unittest.cc
+++ b/pc/localaudiosource_unittest.cc
@@ -10,12 +10,8 @@
 
 #include "pc/localaudiosource.h"
 
-#include <string>
-#include <vector>
-
-#include "media/base/fakemediaengine.h"
-#include "media/base/fakevideorenderer.h"
-#include "rtc_base/gunit.h"
+#include "absl/types/optional.h"
+#include "test/gtest.h"
 
 using webrtc::LocalAudioSource;