<i18n dev> RFR: 8300093: Refactor code examples to use @snippet in java.text.MessageFormat

[Justin Lu]

This PR implements _JEP 413: Code Snippets in Java API Documentation_ for [java.text.MessageFormat](https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/text/class-use/MessageFormat.html).

Code examples using <pre> ... </pre> blocks are replaced with the @ snippet syntax where applicable.

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Commit messages:
 - Switch code blocks with snippet

Changes: https://git.openjdk.org/jdk/pull/12001/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12001&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300093
  Stats: 24 lines in 1 file changed: 12 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/12001.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12001/head:pull/12001

PR: https://git.openjdk.org/jdk/pull/12001