Bump haml from 6.3.0 to 6.4.0 (#360)

Bumps [haml](https://haml.info) from 6.3.0 to 6.4.0.

---
updated-dependencies:
- dependency-name: haml
  dependency-version: 6.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile

@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 
 ruby '2.6.10'
 
-gem 'haml', '~> 6.3'
+gem 'haml', '~> 6.4'
 gem 'iso-639', '~> 0.3.8'
 gem 'json', '~> 2.7'
 gem 'mail', '~> 2.9'

Gemfile.lock

@@ -18,7 +18,7 @@ GEM
     fugit (1.11.2)
       et-orbi (~> 1, >= 1.2.11)
       raabro (~> 1.4)
-    haml (6.3.0)
+    haml (6.4.0)
       temple (>= 0.8.2)
       thor
       tilt
@@ -131,7 +131,7 @@ PLATFORMS
 
 DEPENDENCIES
   byebug
-  haml (~> 6.3)
+  haml (~> 6.4)
   iso-639 (~> 0.3.8)
   json (~> 2.7)
   mail (~> 2.9)