Allow admins to delete sample notes

[s-andrews]

The facility would like the ability to delete notes added to samples.

[s-andrews]

This will require an additional database permission.

GRANT DELETE on sierra.sample_note TO sierrauser@localhost;
FLUSH PRIVILEGES;

or on production:

GRANT DELETE on sierra.sample_note TO sierrauser@bioinform.babraham.ac.uk;
FLUSH PRIVILEGES;

[s-andrews]

I've rolled this out into production and have checked that it seems to be working.