Clean BUILD.gn files: remove extra :memory

Use //third_party/abseil-cpp/absl/memory instead of
//third_party/abseil-cpp/absl/memory:memory in BUILD.gn files.

Bug: None
Change-Id: I47c915f0847b102b37c5b38009c91b315cd3a1b8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128615
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27222}

modules/video_coding/BUILD.gn

@@ -549,7 +549,7 @@ if (rtc_include_tests) {
       "../../rtc_base:checks",
       "../../rtc_base:rtc_base_approved",
       "../../test:test_support",
-      "//third_party/abseil-cpp/absl/memory:memory",
+      "//third_party/abseil-cpp/absl/memory",
     ]
   }