Remove duplicate tests from TestGetDistForGoals

A previous change duplicated the test cases from TestGetDistForGoals()
to test the getDistContributions() method. This change removes the
duplicate tests and leaves a single test to verify that
GetDistForGoals() uses getDistContributions() and
generateDistContributionsForMake() correctly.

Test: m nothing
Bug: 174226317
Change-Id: I545501016b932f9af0d5fda2f452a3a09932d3fb