RFR: JDK-8264419: Remove has_max_index argument from G1BlockOffsetTablePart::block_at_or_preceding

[Ivan Walulya]

Please review this small change to remove superfluous function arguments. 

Testing: tier1

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Commit messages:
 - hange comment
 - refactor

Changes: https://git.openjdk.java.net/jdk/pull/4755/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4755&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264419
  Stats: 14 lines in 2 files changed: 0 ins; 7 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4755.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4755/head:pull/4755

PR: https://git.openjdk.java.net/jdk/pull/4755