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

[Calvin Cheung]

On Thu, 7 Apr 2022 16:22:24 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Please review this simple change for replacing an `if` block with an `assert`.
>> 
>> Passed CI tiers 1 and 2 testing.
>
> Marked as reviewed by iklam (Reviewer).

@iklam Thanks for the review.

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