RFR: 8209992: Align SSLSocket and SSLEngine Javadocs

[Artur Barashev]

Add a javadoc paragraph to SSLSocket.startHandshake() and SSLEngine.beginHandshake() methods explaining behavioral differences between TLSv1.3+ and TLSv1.2- versions.

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Commit messages:
 - 8209992: Align SSLSocket and SSLEngine Javadocs

Changes: https://git.openjdk.org/jdk/pull/26484/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26484&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8209992
  Stats: 11 lines in 2 files changed: 8 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/26484.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26484/head:pull/26484

PR: https://git.openjdk.org/jdk/pull/26484