RFR: 8323645: Remove unused internal sun.net.www.protocol.jar.URLJarFileCallBack interface

[Jaikiran Pai]

Can I please get a review of this change which removes unused code from `sun.net.www.protocol.jar.URLJarFile` and removes `sun.net.www.protocol.jar.URLJarFileCallBack`?

As noted in the linked issue https://bugs.openjdk.org/browse/JDK-8323645 the `sun.net.www.protocol.jar.URLJarFileCallBack` was relevant and used only by Java Plugin code (the "deploy" module in JDK 8) which hasn't been in the JDK for several releases now. Effectively this interface and its sole usage in an internal class of the JDK has been a leftover.

The commit in this PR removes that leftover code. No new tests have been added, given the nature of this change. tier1, tier2, tier3 continue to pass with this change.

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Commit messages:
 - 8323645: Remove unused internal sun.net.www.protocol.jar.URLJarFileCallBack interface

Changes: https://git.openjdk.org/jdk/pull/17396/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17396&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323645
  Stats: 118 lines in 2 files changed: 1 ins; 91 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/17396.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17396/head:pull/17396

PR: https://git.openjdk.org/jdk/pull/17396