RFR: 8336412: sun.net.www.MimeTable has a few unused methods

[Volkan Yazıcı]

Cleans up `sun.net.www.MimeTable`:

* Removes unused methods & variables
* Removes commented out code
* Simplifies iterations over arrays

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Commit messages:
 - Clean up `sun.net.www.MimeTable`

Changes: https://git.openjdk.org/jdk/pull/22831/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22831&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336412
  Stats: 113 lines in 1 file changed: 1 ins; 103 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/22831.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22831/head:pull/22831

PR: https://git.openjdk.org/jdk/pull/22831