RFR: 8264548: Dependencies: ClassHierarchyWalker::is_witness() cleanups

[Vladimir Kozlov]

On Wed, 31 Mar 2021 21:47:53 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> Simplify `ClassHierarchyWalker::is_witness()`.
> 
> Testing: hs-tier1 - hs-tier4.

Looks like it has changes from: https://git.openjdk.java.net/jdk/pull/3293

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Changes requested by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3297