RFR: 8375183: Remove unused SSLConfiguration.maximumProtocolVersion variable

[Artur Barashev]

"SSLConfiguration.maximumProtocolVersion" is not being used in practice. It's used to initialize "TransportContext.protocolVersion" which is being later set to the negotiated protocol before being ever accessed.

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Commit messages:
 - 8375183: Remove unused SSLConfiguration.maximumProtocolVersion variable

Changes: https://git.openjdk.org/jdk/pull/29192/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29192&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375183
  Stats: 20 lines in 2 files changed: 0 ins; 18 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29192.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29192/head:pull/29192

PR: https://git.openjdk.org/jdk/pull/29192