support Nextcloud 21 (fixes #108)

Author: timar

appinfo/info.xml

@@ -44,7 +44,7 @@ Of course, alternatively you could increase memory usage and PHP time-outs by de
     <screenshot>https://www.collaboraoffice.com/downloads/nextcloud/richdocumentscode/collabora-online-screenshot-4.png</screenshot>
     <screenshot>https://www.collaboraoffice.com/downloads/nextcloud/richdocumentscode/collabora-online-screenshot-5.png</screenshot>
     <dependencies>
-        <nextcloud min-version="19" max-version="20"/>
+        <nextcloud min-version="19" max-version="21"/>
         <architecture>x86_64</architecture>
     </dependencies>
     <settings>