RFR: JDK-8289917: Metadata for regionsRefilled of G1EvacuationStatistics event is wrong

[Ralf Schmelter]

This changes the type and description of the regionsRefilled entry.

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Commit messages:
 - Fixed regionsFilled entry

Changes: https://git.openjdk.org/jdk/pull/9448/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9448&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289917
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9448.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9448/head:pull/9448

PR: https://git.openjdk.org/jdk/pull/9448