Fix the error string of the downgrade error

Same as ag/13732406.

Fix tests since we move version code checking into package verification.

Note we use either().or() since GkiInstallTest might run on a branch
that doesn't include ag/13737388.

Bug: 183374149
Test: atest GkiInstallTest
Change-Id: Ieacd65622a304786c6cfbf1ab6435b6f1edd6a7c
1 file changed