RFR: 8268387: Rename maximum compaction to maximal compaction in G1

[Stephanie Crater]

Please review this small change to address Issue [JDK-8268387]( https://bugs.openjdk.java.net/browse/JDK-8268387)

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Commit messages:
 - Rename maximum compaction to maximal compaction

Changes: https://git.openjdk.java.net/jdk/pull/6982/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6982&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268387
  Stats: 21 lines in 6 files changed: 0 ins; 0 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6982.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6982/head:pull/6982

PR: https://git.openjdk.java.net/jdk/pull/6982