drop support for 'retainData' configuration

config/config.example.js

@@ -231,26 +231,17 @@ module.exports = {
      */
     inactiveTime: 90, // days
 
-    /*  CryptPad can be configured to remove inactive data which has not been pinned.
-     *  Deletion of data is always risky and as an operator you have the choice to
-     *  archive data instead of deleting it outright. Set this value to true if
-     *  you want your server to archive files and false if you want to keep using
-     *  the old behaviour of simply removing files.
+    /*  CryptPad archives some data instead of deleting it outright.
+     *  This archived data still takes up space and so you'll probably still want to
+     *  remove these files after a brief period.
+     *
+     *  cryptpad/scripts/evict-inactive.js is intended to be run daily
+     *  from a crontab or similar scheduling service.
      *
-     *  WARNING: this is not implemented universally, so at the moment this will
-     *  only apply to the removal of 'channels' due to inactivity.
-     */
-    retainData: true,
-
-    /*  As described above, CryptPad offers the ability to archive some data
-     *  instead of deleting it outright. This archived data still takes up space
-     *  and so you'll probably still want to remove these files after a brief period.
      *  The intent with this feature is to provide a safety net in case of accidental
      *  deletion. Set this value to the number of days you'd like to retain
      *  archived data before it's removed permanently.
      *
-     *  If 'retainData' is set to false, there will never be any archived data
-     *  to remove.
      */
     archiveRetentionTime: 15,