[jdk20] RFR: 8300953: ClassDesc::ofInternalName missing @since tag

[Adam Sotona]

ClassDesc::ofInternalName was added in JDK 20, however @since tag is missing. 
This patch fixes the javadoc. 

Please review.

Thanks,
Adam

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Commit messages:
 - 8300953: ClassDesc::ofInternalName missing @since tag

Changes: https://git.openjdk.org/jdk20/pull/115/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=115&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300953
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk20/pull/115.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/115/head:pull/115

PR: https://git.openjdk.org/jdk20/pull/115