b5938: Remove invalid sym link and add crontab comment

configuration/crontab

@@ -1,2 +1,3 @@
 * * * * *	export PATH=/bin:/usr/bin:/usr/local/bin; sleep $(( $RANDOM * 60 / 32768 )); update_authorized_keys_for_landscape_managers_if_changed $( cat /root/ssh-key-reader.token ) https://security-service.sapsailing.com /root 2>&1 >>/var/log/sailing.err
 * * * * *	export PATH=/bin:/usr/bin:/usr/local/bin; switchoverArchive.sh /etc/httpd/conf.d/000-macros.conf 2 9 
+#NOTICE: Please try to reference the customised crontabs at $GIT_HOME/configuration/crontabs. This file has been maintained for continuity, but is deprecated.

configuration/crontabs/crontab-mongo

@@ -1 +0,0 @@
-../mongo_instance_setup/crontab