Include absl/memory/memory.h if absl::make_unique is used

Tbr: kwiberg@webrtc.org
Bug: None
Change-Id: Iaf4533d2ce0e80b351a8a664ef8cf7ba0e5ec583
Reviewed-on: https://webrtc-review.googlesource.com/c/115746
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Yves Gerey <yvesg@google.com>
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26168}

call/BUILD.gn

@@ -506,6 +506,7 @@ if (rtc_include_tests) {
       "../test:test_main",
       "../test:test_support",
       "//testing/gtest",
+      "//third_party/abseil-cpp/absl/memory",
     ]
   }
 }