cleanup a line for remove PointerEvent flag

Remove a line missed when removing enable-pointer-event
flag. Related cl:

https: //codereview.chromium.org/2921923002
Bug: 687976
Change-Id: I1d129b05fce79a565ff9a92493d2e16c2d383cf8
Reviewed-on: https://chromium-review.googlesource.com/596689Reviewed-by: Charlie Reis <creis@chromium.org>
Commit-Queue: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491426}

content/public/common/content_features.h

@@ -59,7 +59,6 @@ CONTENT_EXPORT extern const base::Feature kParallelDownloading;
 CONTENT_EXPORT extern const base::Feature kPassiveDocumentEventListeners;
 CONTENT_EXPORT extern const base::Feature kPassiveEventListenersDueToFling;
 CONTENT_EXPORT extern const base::Feature kPepper3DImageChromium;
-CONTENT_EXPORT extern const base::Feature kPointerEvents;
 CONTENT_EXPORT extern const base::Feature kPurgeAndSuspend;
 CONTENT_EXPORT extern const base::Feature kRafAlignedMouseInputEvents;
 CONTENT_EXPORT extern const base::Feature kRafAlignedTouchInputEvents;