RFR: 8280823: Remove NULL check in DumpTimeClassInfo::is_excluded

[Yumin Qi]

On Thu, 27 Jan 2022 19:25:35 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> Please review this trivial change. The NULL check is not needed anymore because the ``DumpTimeClassInfo::_klass` field is never set to NULL.
> 
> Passed Oracle IT tiers 1~4

Marked as reviewed by minqi (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/7249