RFR: 8280070: G1: Fix template parameters in G1SegmentedArraySegment

[Hamlin Li]

This is a simple fix of template parameters in G1SegmentedArraySegment.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.java.net/jdk/pull/7114/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7114&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280070
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7114.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7114/head:pull/7114

PR: https://git.openjdk.java.net/jdk/pull/7114