GN: Do not use forward_dependent_configs_from variable.

It is deprecated and public_deps should be used instead, which will have
the
same effect.

BUG=None
R=brettw@chromium.org,kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/1365063004

Cr-Commit-Position: refs/heads/master@{#10074}

webrtc/modules/audio_coding/BUILD.gn

@@ -693,8 +693,9 @@ source_set("webrtc_opus") {
     configs += [ "../..:common_config" ]
     public_configs = [ "../..:common_inherited_config" ]
 
-    deps += [ rtc_opus_dir ]
-    forward_dependent_configs_from = [ rtc_opus_dir ]
+    public_deps = [
+      rtc_opus_dir,
+    ]
   } else if (build_with_mozilla) {
     include_dirs = [ getenv("DIST") + "/include/opus" ]
   }