Fixed description and keywords on Ubuntu installation docs

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
command line nit
Merge pull request #5886 from financeCoding/mac_doc_nit

command line nit
Merge pull request #5882 from jamtur01/ubfix

Fixed description and keywords on Ubuntu installation docs
removing extra $

Docker-DCO-1.1-Signed-off-by: Adam Singer <financeCoding@gmail.com>
(github: financeCoding)