Revert "Temporarily disable building feedv2"

This reverts commit 9479572b.

Reason for revert: This change was meant to be reverted immediately.

Original change's description:
> Temporarily disable building feedv2
>
> Feedv2 was enabled in June, and now Pinpoint is having merge conflicts
> when rebasing new patches onto pre-Elements base commits. The purpose
> of this CL is to provide a more recent no-Elements base commit for perf
> testing.
>
> I will revert this change as soon as it lands.
>
> Change-Id: I901ce90cd244a28d3213f377e9348c323cad9089
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2453804
> Commit-Queue: Ian Wells <iwells@chromium.org>
> Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#814505}

TBR=carlosk@chromium.org,iwells@chromium.org

Change-Id: I798dfaa48c742571788e6a287050e16aa0c77b18
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2453373Reviewed-by: Ian Wells <iwells@chromium.org>
Commit-Queue: Ian Wells <iwells@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814523}

components/feed/features.gni

@@ -14,7 +14,7 @@ declare_args() {
   enable_feed_v1 = is_android
 
   # Whether version 2 of the NTP feed is enabled in the build.
-  enable_feed_v2 = false
+  enable_feed_v2 = is_android
 }
 
 if (is_android && android_channel != "default") {