Bug 31051: Fix test

Bug 31051: Fix test

When savings ends with a "0"

koha_1       |     #   Failed test 'Savings correctly calculated from current issues'
koha_1       |     #   at t/db_dependent/Koha/Patron.t line 1380.
koha_1       |     #          got: '34583.70'
koha_1       |     #     expected: '34583.7'
koha_1       |
koha_1       |     #   Failed test 'Savings correctly calculated from current and old issues'
koha_1       |     #   at t/db_dependent/Koha/Patron.t line 1385.
koha_1       |     #          got: '34583.70'
koha_1       |     #     expected: '34583.7'
koha_1       |     # Looks like you failed 2 tests of 4.
koha_1       |
koha_1       | #   Failed test 'get_savings tests'
koha_1       | #   at t/db_dependent/Koha/Patron.t line 1388.
koha_1       | # Looks like you failed 1 test of 20.
koha_1       | [00:07:57] t/db_dependent/Koha/Patron.t

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>