Remove use of deprecated `scan_plugins` method 
Remove use of deprecated `scan_plugins` method 

`scan_plugins` has been deprecated in favour of `scan_plugins_regex`. This 
is causing warnings to be logged.

The new method takes a regular expression as its first argument, rather than a 
simple prefix string. This commit adds a regular expression which does the same 
thing as the prefix argument used to do.

For source code see: https://lml.readthedocs.io/en/latest/_modules/lml/loader.html
chfw/pyexcel,chfw/pyexcel