[jdk19] RFR: 8290209: jcup.md missing additional text

[Joe Wang]

Update jcup.md with additional text at the end. Refer to http://www2.cs.tum.edu/projects/cup/licence.php.

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Commit messages:
 - 8290209: jcup.md missing additional text

Changes: https://git.openjdk.org/jdk19/pull/141/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=141&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290209
  Stats: 11 lines in 1 file changed: 9 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk19/pull/141.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/141/head:pull/141

PR: https://git.openjdk.org/jdk19/pull/141