feat: Support for JWT 3.x (#542)

Author: dazuma

googleauth.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |gem|
   gem.add_dependency "faraday", ">= 1.0", "< 3.a"
   gem.add_dependency "google-cloud-env", "~> 2.2"
   gem.add_dependency "google-logging-utils", "~> 0.1"
-  gem.add_dependency "jwt", ">= 1.4", "< 3.0"
+  gem.add_dependency "jwt", ">= 1.4", "< 4.0"
   gem.add_dependency "multi_json", "~> 1.11"
   gem.add_dependency "os", ">= 0.9", "< 2.0"
   gem.add_dependency "signet", ">= 0.16", "< 2.a"