RFR: 8347370: Unnecessary Hashtable usage in javax.swing.text.html.HTML

[Andrey Turbanov]

The Hashtable `javax.swing.text.html.HTML.scMapping` is modified only within `<clinit>` block.
We can replace it with immutable map to avoid Hashtable synchronization overhead.

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Commit messages:
 - 8347370 update copyright year
 - [PATCH] Unnecessary Hashtable usage in javax.swing.text.html.HTML.scMapping

Changes: https://git.openjdk.org/jdk/pull/21842/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21842&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347370
  Stats: 20 lines in 1 file changed: 10 ins; 8 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21842.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21842/head:pull/21842

PR: https://git.openjdk.org/jdk/pull/21842