Upgrade haml-lint to 0.30.0

This also supports Ruby 2.6.

Gemfile

@@ -356,7 +356,7 @@ group :development, :test do
   gem 'rubocop-rspec', '~> 1.22.1'
 
   gem 'scss_lint', '~> 0.56.0', require: false
-  gem 'haml_lint', '~> 0.28.0', require: false
+  gem 'haml_lint', '~> 0.30.0', require: false
   gem 'simplecov', '~> 0.14.0', require: false
   gem 'bundler-audit', '~> 0.5.0', require: false
 

Gemfile.lock

@@ -358,7 +358,7 @@ GEM
     haml (5.0.4)
       temple (>= 0.8.0)
       tilt
-    haml_lint (0.28.0)
+    haml_lint (0.30.0)
       haml (>= 4.0, < 5.1)
       rainbow
       rake (>= 10, < 13)
@@ -1081,7 +1081,7 @@ DEPENDENCIES
   graphiql-rails (~> 1.4.10)
   graphql (~> 1.8.0)
   grpc (~> 1.19.0)
-  haml_lint (~> 0.28.0)
+  haml_lint (~> 0.30.0)
   hamlit (~> 2.8.8)
   hangouts-chat (~> 0.0.5)
   hashie-forbidden_attributes