[jdk19] RFR: 8290207: Missing notice in dom.md

[Joe Wang]

Update dom.md, adding notice.

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Commit messages:
 - 8290207: Missing notice in dom.md

Changes: https://git.openjdk.org/jdk19/pull/138/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=138&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290207
  Stats: 15 lines in 1 file changed: 15 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk19/pull/138.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/138/head:pull/138

PR: https://git.openjdk.org/jdk19/pull/138