Update settings.env

switch from mysql to postgresql

examples/bitwarden-unified/settings.env

@@ -7,7 +7,7 @@ BW_DOMAIN=bitwarden.example.com
 
 # Database
 # Available providers are sqlserver, postgresql, or mysql/mariadb
-BW_DB_PROVIDER=mysql
+BW_DB_PROVIDER=postgresql
 BW_DB_SERVER=db
 BW_DB_DATABASE=bitwarden_vault
 BW_DB_USERNAME=bitwarden