RFR: 8339020: Remove unused HeapShared::calculate_oopmap

[Coleen Phillimore]

On Wed, 28 Aug 2024 18:59:34 GMT, Matias Saavedra Silva <matsaave at openjdk.org> wrote:

> After JDK-8251330, `HeapShared::calculate_oopmap` is totally unused so this patch removes the method. Verified with tier1-4 tests.

Looks good plus trivial.

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Marked as reviewed by coleenp (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20753#pullrequestreview-2270117766