LyricWiki: link to the actual lyrics page

Summary:
Instead of pointing to the homepage of the wiki,
set the link to the actual page of the lyrics
which are being shown.

BUG: 332664
FIXED-IN: 18.12.0

Test Plan:
The link to the LyricsWiki points to the actual page.
Nothing changes when the lyrics are not found.

Reviewers: mpyne

Reviewed By: mpyne

Differential Revision: https://phabricator.kde.org/D15303