Fix `Should -Throw` to handle expected message with escaped wildcard (backport)

[johlju]

PR Summary

This target v5. This resolves #2558 so that when the expected message containing escaped wildcard is output is removes the escaped character so it shows the correct expected message that differ from the actual value.

Part of issue #2558

PR Checklist

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[johlju]

Okay, that was not correct. Know what I did wrong. Trying again.

[johlju]

Reverted to tag 5.6.1 and rebase to rel/5.6.x. Looks good now.