Revert "Make sure Chromium will pick the correct field_trial/metric impl."

This reverts commit 8dc280d804bc49932f429955b27ff385054ddfa0.

Reason for revert: Breaks NDK compile on Chrome bots: https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8932231862774278176/+/steps/compile__with_patch_/0/stdout 
Original change's description:
> Make sure Chromium will pick the correct field_trial/metric impl.
> 
> Chromium wants to pick its own field_trial and metrics implementation,
> and WebRTC has an escape hatch to let it remove the definition of these
> symbols. This obviously causes liker errors if Chromium will not pick
> the correct dependency (which cannot be forced by GN check since there
> is no header inclusion).
> 
> Instead of hoping that the build target with the correct implementation
> will be added as a dependency somewhere in the build graph, this CL
> wants to explicitly add the dependency as close as possible to the
> headers, so if they are included and WebRTC is built as part of Chromium
> the correct implementation will be linked into the binary.
> 
> Bug: webrtc:9631
> Change-Id: I2d1cfe541726341adfdf81e14e036464aa003d4d
> Reviewed-on: https://webrtc-review.googlesource.com/c/107040
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25269}

TBR=mbonadei@webrtc.org,kwiberg@webrtc.org

Change-Id: I4c04b60d198aa1b89278083d518bfa93c15d09bb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9631
Reviewed-on: https://webrtc-review.googlesource.com/c/107140
Reviewed-by: Niklas Enbom <niklas.enbom@webrtc.org>
Commit-Queue: Niklas Enbom <niklas.enbom@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25275}
diff --git a/system_wrappers/BUILD.gn b/system_wrappers/BUILD.gn
index c225224..0f5dc14 100644
--- a/system_wrappers/BUILD.gn
+++ b/system_wrappers/BUILD.gn
@@ -105,11 +105,6 @@
   if (rtc_exclude_field_trial_default) {
     defines = [ "WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT" ]
   }
-  if (build_with_chromium) {
-    deps = [
-      "../../webrtc_overrides:field_trial",
-    ]
-  }
 }
 
 rtc_source_set("metrics") {
@@ -128,9 +123,6 @@
     "../rtc_base:checks",
     "../rtc_base:rtc_base_approved",
   ]
-  if (build_with_chromium) {
-    deps += [ "../../webrtc_overrides:metrics" ]
-  }
 }
 
 if (is_android && !build_with_mozilla) {