Use new compact OARS syntax

There's a shiny new syntax for "nope, I don't do any of these", as of
hughsie/oars#17, so let's use it.

Author: kaiw

data/org.gnome.meld.appdata.xml.in

@@ -46,33 +46,5 @@
   <project_group>GNOME</project_group>
   <_developer_name>The GNOME Project</_developer_name>
   <translation type="gettext">meld</translation>
-  <content_rating type="oars-1.1">
-    <content_attribute id="violence-cartoon">none</content_attribute>
-    <content_attribute id="violence-fantasy">none</content_attribute>
-    <content_attribute id="violence-realistic">none</content_attribute>
-    <content_attribute id="violence-bloodshed">none</content_attribute>
-    <content_attribute id="violence-sexual">none</content_attribute>
-    <content_attribute id="violence-desecration">none</content_attribute>
-    <content_attribute id="violence-slavery">none</content_attribute>
-    <content_attribute id="violence-worship">none</content_attribute>
-    <content_attribute id="drugs-alcohol">none</content_attribute>
-    <content_attribute id="drugs-narcotics">none</content_attribute>
-    <content_attribute id="drugs-tobacco">none</content_attribute>
-    <content_attribute id="sex-nudity">none</content_attribute>
-    <content_attribute id="sex-themes">none</content_attribute>
-    <content_attribute id="sex-homosexuality">none</content_attribute>
-    <content_attribute id="sex-prostitution">none</content_attribute>
-    <content_attribute id="sex-adultery">none</content_attribute>
-    <content_attribute id="sex-appearance">none</content_attribute>
-    <content_attribute id="language-profanity">none</content_attribute>
-    <content_attribute id="language-humor">none</content_attribute>
-    <content_attribute id="language-discrimination">none</content_attribute>
-    <content_attribute id="social-chat">none</content_attribute>
-    <content_attribute id="social-info">none</content_attribute>
-    <content_attribute id="social-audio">none</content_attribute>
-    <content_attribute id="social-location">none</content_attribute>
-    <content_attribute id="social-contacts">none</content_attribute>
-    <content_attribute id="money-purchasing">none</content_attribute>
-    <content_attribute id="money-gambling">none</content_attribute>
-  </content_rating>
+  <content_rating type="oars-1.1" />
 </component>