Removed link to Installation Guide from UI 'About' screen.

[ci skip]

https://bugzilla.redhat.com/show_bug.cgi?id=1145326
https://bugzilla.redhat.com/show_bug.cgi?id=1144483
Merge pull request #674 from h-kataria/removed_installation_guide_link

Removed link to Installation Guide from UI 'About' screen.