RFR: 8348089: Serial: Remove virtual specifier in SerialHeap

Mon Jan 20 10:22:08 UTC 2025

Trivial removing unused `virtual` specifier and move `protected` methods to `private`.

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Commit messages:
 - virtual

Changes: https://git.openjdk.org/jdk/pull/23196/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23196&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348089
  Stats: 7 lines in 1 file changed: 3 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23196.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23196/head:pull/23196

PR: https://git.openjdk.org/jdk/pull/23196