Fix and ammend gemspec metadata (#19419)
Fix and ammend gemspec metadata (#19419)

* Fix and ammend gemspec metadata

`docs_url` is called `documentation_uri`. Right now, RubyGems.org [0]
links to RubyDoc.info [1] instead of the URL previously set in
`docs_url`.

The other keys were set to show what could be done to also show up
on RubyGems.org. While there is no "mailing list", I think GitHub
discussions are the closest thing.

Happy to add, change, remove any attributes that are unwanted. See the
`metadata` docs [2] for the possible keys.

[0] https://rubygems.org/gems/fastlane
[1] https://www.rubydoc.info/gems/fastlane/2.195.0
[2] https://guides.rubygems.org/specification-reference/#metadata

* Remove `mailing_list_uri` from gemspec `metadata`

Co-authored-by: Josh Holtz <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@joshholtz.com>

Co-authored-by: Josh Holtz <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@joshholtz.com>
KrauseFx/fastlane,nafu/fastlane,nafu/fastlane,KrauseFx/fastlane,KrauseFx/fastlane,KrauseFx/fastlane,lacostej/fastlane,fastlane/fastlane,fastlane/fastlane,KrauseFx/fastlane,bassrock/fastlane,KrauseFx/fastlane,icecrystal23/fastlane,fastlane/fastlane,nafu/fastlane,lacostej/fastlane,fastlane/fastlane,icecrystal23/fastlane,bassrock/fastlane,nafu/fastlane,lacostej/fastlane,icecrystal23/fastlane,lacostej/fastlane,bassrock/fastlane,nafu/fastlane,bassrock/fastlane,fastlane/fastlane,icecrystal23/fastlane,icecrystal23/fastlane,icecrystal23/fastlane,bassrock/fastlane,nafu/fastlane,lacostej/fastlane,bassrock/fastlane,KrauseFx/fastlane,fastlane/fastlane,nafu/fastlane,lacostej/fastlane