[jdk19] RFR: JDK-8289399: Update SourceVersion to use snippets

[Joe Darcy]

Please review this simple doc update.

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Commit messages:
 - JDK-8289399: Update SourceVersion to use snippets

Changes: https://git.openjdk.org/jdk19/pull/87/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=87&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289399
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk19/pull/87.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/87/head:pull/87

PR: https://git.openjdk.org/jdk19/pull/87