Worksheet templates converted to V6

Converted to V6 by opening and saving using '5.99.0-12088-gff9612b6da Build Date: Aug 26 2021 20:58:53'. No changes are made to the templates.

After this conversion, this message is no longer displayed when the templates are opened:

This is part of issue #29 (closed)

There's a similar issue with the built in templates in Eeschema, see kicad/code/kicad#9039 (closed)