Use the SPDX identifier for the license

https://spdx.org/licenses/ As recommended in the Rubygems.org guide: https://guides.rubygems.org/specification-reference/#license=

Author: orien

zendesk_api.gemspec

@@ -11,7 +11,7 @@ Gem::Specification.new do |s|
  s.homepage = "https://developer.zendesk.com"
  s.summary = 'Zendesk REST API Client'
  s.description = 'Ruby wrapper for the REST API at https://www.zendesk.com. Documentation at https://developer.zendesk.com.'
- s.license = 'Apache License Version 2.0'
+ s.license = 'Apache-2.0'
 
  s.metadata = {
  'bug_tracker_uri' => 'https://github.com/zendesk/zendesk_api_client_rb/issues',