lib/sql: Update grant script for recent schema changes

lib/sql: Update grant script for recent schema changes

This change fixes a few omissions in the grant scripts:

- patchrelation is missing from both mysql and postgres scripts; it's
  only needed for web user access.

- event is missing from the web grants on postgres, and the mail grants
  on mysql.

Tested on postgres only.

Fixes: 27c2acf56c ("models, templates: Add patch relations")
Fixes: 34e3c9c493 ("sql: Update 'grant-all.mysql' script with missing tables")
Fixes: 234bc7c316 ("lib/sql: fix permissions for v2.0.0 on postgres")
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Daniel Axtens <dja@axtens.net>