RFR: 8330699: Obsolete -XX:+UseEmptySlotsInSupers

[Coleen Phillimore]

Remove code to not use empty slots in supers.
Tested with tier1-4.

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Commit messages:
 - 8330699: Obsolete -XX:+UseEmptySlotsInSupers

Changes: https://git.openjdk.org/jdk/pull/19720/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19720&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330699
  Stats: 99 lines in 3 files changed: 0 ins; 97 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19720.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19720/head:pull/19720

PR: https://git.openjdk.org/jdk/pull/19720