RFR: Fix off-by-one error when handling pinned regions in a mixed collection [v2]

[Y. Srinivas Ramakrishna]

On Thu, 16 Mar 2023 03:27:53 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This fixes an off-by-one error that manifested when the first mixed collection candidate was pinned.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove over aggressive asserts, improve readability

Marked as reviewed by ysr (Author).

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

PR: https://git.openjdk.org/shenandoah/pull/226