fixup! Firefox preference overrides.

Bug 42315: Drop dom.enable_event_timing.

It is already protected by RFP.

browser/app/profile/001-base-profile.js

@@ -395,8 +395,6 @@ pref("network.http.referer.XOriginTrimmingPolicy", 2); // Bug 17228: Force trim
 pref("media.videocontrols.picture-in-picture.enabled", false); // Bug 40148: disable until audited in #40147
 // Bug 40463: Disable Windows SSO
 pref("network.http.windows-sso.enabled", false, locked);
-// Bug 40383: Disable new PerformanceEventTiming
-pref("dom.enable_event_timing", false);
 // Disable API for measuring text width and height.
 pref("dom.textMetrics.actualBoundingBox.enabled", false);
 pref("dom.textMetrics.baselines.enabled", false);