spec/ruby/library/yaml: Test YAML.unsafe_load instead of YAML.load in 3.1

Author: mame

lib/mspec/matchers/match_yaml.rb

@@ -30,7 +30,11 @@ def clean_yaml(yaml)
   def valid_yaml?(obj)
     require 'yaml'
     begin
-      YAML.load(obj)
+      if defined?(YAML.unsafe_load)
+        YAML.unsafe_load(obj)
+      else
+        YAML.load(obj)
+      end
     rescue
       false
     else