Remove tracking of src:epiphany-browser for CVE-2019-6251

The issue is in webkit2gtk and was adressed there[1]. Updated
description to "WebKitGTK and WPE WebKit prior to version 2.24.1 are
vulnerable to address bar spoofing upon certain JavaScript redirections.
An attacker could cause malicious web content to be displayed as if for
a trusted URI."

 [1] https://gitlab.gnome.org/GNOME/epiphany/issues/532