RFR: 8302047: G1: Remove unused G1RegionToSpaceMapper::_region_granularity

[Thomas Schatzl]

On Wed, 8 Feb 2023 08:42:25 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial removing dead code.

Lgtm and trivial

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.org/jdk/pull/12469