Turn rtc::{Make,Wrap}Unique into aliases for their Abseil counterparts

We don't want to maintain our own versions. This CL is step one in
getting rid of them.

Bug: webrtc:9473
Change-Id: Ib8a54288509f4768b482367b738224869a5af559
Reviewed-on: https://webrtc-review.googlesource.com/86282
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23786}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 28ff3c8..716d0b2 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -123,6 +123,9 @@
     "ptr_util.h",
     "scoped_ref_ptr.h",
   ]
+  deps = [
+    "//third_party/abseil-cpp/absl/memory",
+  ]
 }
 
 rtc_source_set("refcount") {