RFR: 8272629: G1: simplify G1GCParPhaseTimesTracker constructor API

[Albert Mingkun Yang]

Simple change of removing an always-true argument in `G1GCParPhaseTimesTracker`.

Test: hotspot_gc

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Commit messages:
 - must-record

Changes: https://git.openjdk.java.net/jdk/pull/5162/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5162&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272629
  Stats: 9 lines in 3 files changed: 0 ins; 4 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5162.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5162/head:pull/5162

PR: https://git.openjdk.java.net/jdk/pull/5162