Bump jwt version max version to 2.6 (#626)

Author: MarcPer

twilio-ruby.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
   spec.extra_rdoc_files = ['README.md', 'LICENSE']
   spec.rdoc_options = ['--line-numbers', '--inline-source', '--title', 'twilio-ruby', '--main', 'README.md']
 
-  spec.add_dependency('jwt', '>= 1.5', '<= 2.5')
+  spec.add_dependency('jwt', '>= 1.5', '<= 2.6')
   spec.add_dependency('nokogiri', '>= 1.6', '< 2.0')
   spec.add_dependency('faraday', '>= 0.9', '< 3.0')
   # Workaround for RBX <= 2.2.1, should be fixed in next version