remove parlour gem from Gemfile

When I first introduced sorbet to this project I used parlour to generate
an RBI file and work with it. However, now that I'm switching to inline
RBS comments for types, I don't think I need it any more.

The `spoom` gem is now my go-to for generating an RBI file for inclusion
in a gem release

Author: yob

Gemfile

@@ -7,7 +7,6 @@ gemspec
 gem "sorbet", "0.5.12381"
 gem "tapioca", "0.17.7", require: false
 gem "spoom"
-gem 'parlour'
 
 # Required by yard. Part of stdlib in older rubies, but on modern rubies it's a gem
 gem "webrick"