RFR: 8282040: Remove unnecessary check made obsolete by JDK-8261941

[Ioi Lam]

On Thu, 7 Apr 2022 00:27:38 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

> Please review this simple change for replacing an `if` block with an `assert`.
> 
> Passed CI tiers 1 and 2 testing.

LGTM. I think this PR can be treated as a trivial change.

-------------

PR: https://git.openjdk.java.net/jdk/pull/8133