Test customer report filtering without sorting

The report doesn't seem to sort. So the specs don't expect that either
now. These specs were flaky before, depending on the random order in the
database query result.

spec/lib/reports/customers_report_spec.rb

@@ -266,7 +266,7 @@ module Reporting
                     completed_at_lt: 1.day.after(o2.completed_at)
                   }
                 )
-                expect(subject.filter(orders)).to eq([o2, o3])
+                expect(subject.filter(orders)).to match_array [o2, o3]
               end
 
               it "when completed_at_lt param is missing" do
@@ -276,7 +276,7 @@ module Reporting
                     completed_at_lt: ""
                   }
                 )
-                expect(subject.filter(orders)).to eq([o1, o2])
+                expect(subject.filter(orders)).to match_array [o1, o2]
               end
             end