Add example for ensure=absent

tests/ini_setting.pp

@@ -15,3 +15,11 @@ ini_setting { "sample setting2":
   ensure              => present,
   require             => Ini_setting["sample setting"],
 }
+
+ini_setting { "sample setting3":
+  path                => '/tmp/foo.ini',
+  section             => 'bar',
+  setting             => 'bazsetting',
+  ensure              => absent,
+  require             => Ini_setting["sample setting2"],
+}