Update dependency font-awesome-sass to v6

Author: renovate[bot]

Gemfile

@@ -24,7 +24,7 @@ gem 'acts-as-taggable-on', '~> 9.0.0' # Tags
 gem 'barnes', '~> 0.0.9' # heroku application metrics
 gem 'blazer', '~> 2.5.0' # Business Intelligence made easy
 gem 'commonmarker', '~> 0.23.2' # GitHub Flavored Markdown renderer
-gem 'font-awesome-sass', '~> 5.15.1'
+gem 'font-awesome-sass', '~> 6.3.0'
 gem 'gemoji', '~> 3.0.1' # emoji helpers
 gem 'ginjo-omniauth-slack', '~> 2.5', require: 'omniauth-slack'
 gem 'hamlit', '~> 2.16.0' # Templating language

Gemfile.lock

@@ -134,9 +134,9 @@ GEM
       faraday-net_http (~> 2.0)
       ruby2_keywords (>= 0.0.4)
     faraday-net_http (2.0.1)
-    ffi (1.15.4)
-    font-awesome-sass (5.15.1)
-      sassc (>= 1.11)
+    ffi (1.15.5)
+    font-awesome-sass (6.3.0)
+      sassc (~> 2.0)
     gemoji (3.0.1)
     ginjo-omniauth-slack (2.5.0)
       omniauth-oauth2 (>= 1.4.0)
@@ -427,7 +427,7 @@ DEPENDENCIES
   factory_bot_rails (~> 6.2.0)
   faker (~> 2.20.0)
   faraday (~> 2.2.0)
-  font-awesome-sass (~> 5.15.1)
+  font-awesome-sass (~> 6.3.0)
   gemoji (~> 3.0.1)
   ginjo-omniauth-slack (~> 2.5)
   gon (~> 6.4.0)