RFR: RN-Change is default

[Jesper Wilhelmsson]

Clarification that RN-Change is the default.

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Commit messages:
 - RN-Change is default

Changes: https://git.openjdk.org/guide/pull/99/files
 Webrev: https://webrevs.openjdk.org/?repo=guide&pr=99&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/guide/pull/99.diff
  Fetch: git fetch https://git.openjdk.org/guide pull/99/head:pull/99

PR: https://git.openjdk.org/guide/pull/99