Remove #updateStoredSession (6/n)

Per offline discussion, the mapping between id and session object won't
change over time. There is no need to update the mapping again.

Bug: 167996901
Test: atest StagedInstallTest StagedInstallInternalTest
Change-Id: I24c0d648358d6ffab36a89598c297bdf4f62156e
1 file changed