Linux native notifications: Remove spec_version check

The spec version check was added to blacklist servers that don't
support icons.  However, some servers like xfce4-notifyd list a spec
version that doesn't have icons when the server actually does support
icons.  More context can be found on:
https://codereview.chromium.org/2883983004/

BUG=676220
R=peter@chromium.org,thestig@chromium.org

Review-Url: https://codereview.chromium.org/2891823002
Cr-Commit-Position: refs/heads/master@{#472953}
3 files changed