RFR: 8350808: Small typos in JShell method SnippetEvent.toString()

[Archie Cobbs]

This PR which fixes three small typos in the method `SnippetEvent.toString()`.

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Commit messages:
 - Fix typos in the JShell method SnippetEvent.toString().

Changes: https://git.openjdk.org/jdk/pull/23809/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23809&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350808
  Stats: 67 lines in 2 files changed: 63 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/23809.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23809/head:pull/23809

PR: https://git.openjdk.org/jdk/pull/23809