RFR: 8266018: Shenandoah: fix an incorrect assert

[Roman Kennke]

On Tue, 27 Apr 2021 03:10:52 GMT, wattsun110 <github.com+80801020+wattsun110 at openjdk.org> wrote:

> May I get reviews for this one-line change which fixes an incorrect assert?
> 
> thanks
> watt

Looks good! Thanks for the contribution!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3710