Fix BooleanFileDatastore of Using Set.copyOf()

Set.copyOf() is only available on S+. The issue is discovered in running the unit test on R, and it should also impact on production. The only scenario it hasn't introduced any production issue is because the usage is limited to Fledge API's App Consent flow, which is not enabled on R.

Bug: 335732880
Test: atest AdServicesSharedLibrariesUnitTests on R device. # This will be submitted together with the test mapping change
Change-Id: I08357e02ae39d2a4ba691b683f08c5a8b0809352