RFR: 8337641: G1: Remove unused G1CollectedHeap::alloc_highest_free_region [v2]

[Albert Mingkun Yang]

> Trivial removing dead code.

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20415/files
  - new: https://git.openjdk.org/jdk/pull/20415/files/01b06d59..1ff8da35

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20415&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20415&range=00-01

  Stats: 27 lines in 2 files changed: 0 ins; 27 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20415.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20415/head:pull/20415

PR: https://git.openjdk.org/jdk/pull/20415