Remove redundant checkpoint activation logic in apexd

Checkpoint for staged install is activated during pre-reboot
verification of session, hence activation in apexd is no longer
needed.

Bug: 141843321
Test: atest StagedInstallTest
Test: atest ApexServiceTest
Change-Id: I4b35c8af0384766a8c9e4a44b7b592cb112d9c18
1 file changed