MT#56958 tests: increase timeout for prepaid-costs

We have randomly failing tests (see e.g.
https://jenkins.mgm.sipwise.com/job/rate-o-mat-tests-docker/46684/testReport/):

| <init>.rateomat-10-prepaid-costs_t	0 ms	4
| rateomat-10-prepaid-costs_t.40 - source_customer_cost = 150.000000	0 ms	1
| rateomat-10-prepaid-costs_t.41 - rating_status = ok	0 ms	1
| rateomat-10-prepaid-costs_t.43 - prepaid cost record does not exist	0 ms	1
| rateomat-10-prepaid-costs_t.75 - rating_status = ok	0 ms	1
| rateomat-10-prepaid-costs_t.77 - source_customer_cost = 150.000000	0 ms	1
| rateomat-10-prepaid-costs_t.78 - rating_status = ok	0 ms	1
| rateomat-10-prepaid-costs_t.80 - prepaid cost record does not exist	0 ms	1
| rateomat-10-prepaid-costs_t.73 - source_customer_cost = 150.000000	0 ms	2
| rateomat-10-prepaid-costs_t.76 - prepaid cost record does not exist	0 ms	3
| rateomat-10-prepaid-costs_t.52 - cdrs were all processed	0 ms	4
| rateomat-10-prepaid-costs_t.81 - cdrs were all processed	0 ms	4

This seems to be caused by timing issues on our build infrastructure,
being caused by rateomat getting stopped before it finished
processing. Give the prepaid-costs tests some further time to finish,
at least until we have a better way to handle this situation.

Change-Id: I0320f10a0814e1d51732264ddb6f9940c40ae4b9

t/rateomat-10-prepaid-costs.t

@@ -18,7 +18,7 @@ use Test::More;
 
 local $ENV{RATEOMAT_WRITE_CDR_RELATION_DATA} = 1;
 
-$Utils::Rateomat::rateomat_timeout = 30;
+$Utils::Rateomat::rateomat_timeout = 60;
 
 my $provider = Utils::Api::setup_provider('test.com',
 	[ #rates: