fix: Gemfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-JSON-560838

Author: snyk-bot

Gemfile

@@ -129,7 +129,7 @@ gem 'ruby2_keywords'
 gem 'rubygems-update'
 gem 'sass'
 gem 'sass-listen'
-gem 'sawyer'
+gem 'sawyer', '>= 0.9.3'
 gem 'scss_lint'
 gem 'securerandom'
 gem 'set'