devel/rubygem-graphlient: update to 0.5.0

Required for gitlab-ce 15.0.0.
Changelog:
https://github.com/ashkan18/graphlient/blob/master/CHANGELOG.md

0.5.0 (12/28/2020)

#81: Make graphlient run on ruby 3.0 - @Burgestrand.
#79: Added client testing docs - @GabrielDzul.