Remove unused translation strings

Signed-off-by: Joas Schilling <coding@schilljs.com>

app/src/main/res/values/strings.xml

@@ -179,8 +179,6 @@
     <string name="nc_make_call_private">Make conversation private</string>
     <string name="nc_delete_call">Delete conversation</string>
     <string name="nc_delete">Delete</string>
-    <string name="nc_delete_conversation_default">Please confirm your intent to remove the conversation.</string>
-    <string name="nc_delete_conversation_one2one">If you delete the conversation, it will also be deleted for %1$s.</string>
     <string name="nc_delete_conversation_more">If you delete the conversation, it will also be deleted for all other participants.</string>
 
     <string name="nc_new_conversation">New conversation</string>