Bug 21319: Remove highlight and tooltip on Koha Team version

Bug 21319: Remove highlight and tooltip on Koha Team version

This patch modifies the about page to remove a <span> on the Koha
version number which explained the version numbering change.

To test, apply the patch and view the "Koha team" tab on the about page.
The "Koha 18.05 release team" header should not have the number
highlighted.

Signed-off-by: pierre-marc <pierre-marc.thibault@inLibro.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>