refactor: replace YAML.load_file with YAML.safe_load

replace YAML.load_file with YAML.safe_load for just in case.

lib/ayashige/domain.rb

@@ -59,7 +59,7 @@ def suspicious_words_score
     end
 
     def suspicious
-      @suspicious ||= YAML.load_file File.expand_path("./config/suspicious.yml", __dir__)
+      @suspicious ||= YAML.safe_load File.read(File.expand_path("./config/suspicious.yml", __dir__))
     end
 
     def suspicious_keywords