Move rtc::make_ref_counted to api/

Bug: webrtc:12701
Change-Id: If49095b101c1a1763c2a44a0284c0d670cce953f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/265390
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37219}
diff --git a/pc/proxy_unittest.cc b/pc/proxy_unittest.cc
index 48c087f..ebfde9f 100644
--- a/pc/proxy_unittest.cc
+++ b/pc/proxy_unittest.cc
@@ -13,6 +13,7 @@
 #include <memory>
 #include <string>
 
+#include "api/make_ref_counted.h"
 #include "rtc_base/gunit.h"
 #include "rtc_base/ref_count.h"
 #include "test/gmock.h"