RFR: 8334097: Parallel: Obsolete HeapFirstMaximumCompactionCount

[Albert Mingkun Yang]

Simple obsoleting a Parallel GC product flag.

-------------

Commit messages:
 - pgc-obsolete-first-max-compact

Changes: https://git.openjdk.org/jdk/pull/19673/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19673&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334097
  Stats: 8 lines in 3 files changed: 2 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19673.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19673/head:pull/19673

PR: https://git.openjdk.org/jdk/pull/19673