tweak help for core Change-Id: Ib8ccc9bc52718d9b0ebbfee76ad93dc29c260863

Change-Id: Iffb5f9facb234be10523af93f1e23607fb4fdd1c
Reviewed-on: https://gerrit.libreoffice.org/6663
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>