RFR: 8290018: Remove dead declarations in G1BlockOffsetTablePart

[Thomas Schatzl]

Hi all,

  please review this removal of dead code in `G1BlockOffsetTablePart`.

Testing: compilation

Thanks,
  Thomas

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Commit messages:
 - Initial version

Changes: https://git.openjdk.org/jdk/pull/9429/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9429&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290018
  Stats: 12 lines in 1 file changed: 0 ins; 12 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9429.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9429/head:pull/9429

PR: https://git.openjdk.org/jdk/pull/9429