Add Greek characters to unaccent.rules.
Author: Tasos Maschalidis
Reviewed-by: Michael Paquier, Tom Lane
Discussion: https://postgr.es/m/
153495048900.1368.
11566580687623014380%40wrigleys.postgresql.org
Discussion: https://postgr.es/m/VI1PR01MB38537EBD529FE5EE3FE9A5FEB5370%40VI1PR01MB3853.eurprd01.prod.exchangelabs.com