(maint) Bump to packaging 0.99.8

This commit bumps the packaging gem dependency to be more specific. Without
this, older versions of packaging get pulled in, which don't include necessary
updates for shipping.

Gemfile

@@ -11,9 +11,9 @@ def location_for(place)
 end
 
 gem 'vanagon', *location_for(ENV['VANAGON_LOCATION'] || '~> 0.15.11')
-gem 'packaging', *location_for(ENV['PACKAGING_LOCATION'] || '~> 0.99')
+gem 'packaging', *location_for(ENV['PACKAGING_LOCATION'] || '~> 0.99.8')
 gem 'artifactory'
 gem 'rake'
 gem 'json'
 gem 'octokit'
-gem 'rubocop', "~> 0.34.2"
+gem 'rubocop', "~> 0.34.2"