procmail: Fix license format QA error

Fix the following QA error:

,----
| WARNING: Recipe procmail, LICENSE (GPL-2.0 Artistic-1.0) has invalid
|     format, LICENSES must have operator "([&|() ])" between them.
`----

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>