Remove "orderable" from hst:pages, components and templates

Examining the output of the CMS 12 upgrade verifier, I get irrelevant reordering complaints. I could add .meta:ignore-reordered-children on these OOTB nodes, but that would not help for the project-specific definitions. I'd rather remove the orderable flag from the CND.

Will need to check with Ard if this is sensible for these node types.