Remove unnecessary stripping of __p9k prefix in segment names
Remove unnecessary stripping of __p9k prefix in segment names

Initially this was done because all segments passed their name
as first parameter to p9k::prepareSegment, including custom
segments, which had a __p9k_ prefix. This was changed, custom
segments now pass a cleaned name, hence the check could be
removed.

dritter/powerlevel9k,dritter/powerlevel9k