Merge pull request #39 from ruby-syntax-tree/dependabot/bundler/haml-6.0.4

Bump haml from 6.0.3 to 6.0.4

Author: github-actions[bot]

Gemfile.lock

@@ -10,7 +10,7 @@ GEM
   remote: https://rubygems.org/
   specs:
     docile (1.4.0)
-    haml (6.0.3)
+    haml (6.0.4)
       temple (>= 0.8.2)
       thor
       tilt