Try simplify EqualError in item_hook_handler_test.go

[kaovilai]

To simplify EqualError comparing error to error, rather than string compared to err

/assign me

          I believe it’s out of scope of this PR. This only apply best practices while keeping actual tests working. Maybe you can do a PR following your suggestion in the same time ?

Originally posted by @mmorel-35 in #8027 (comment)

[github-actions]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days. If a Velero team member has requested log or more information, please provide the output of the shared commands.

[kaovilai]

obsolete by #8027 closing.