RFR: 8064931: tools/javac/scope/DupUnsharedTest.java needs to be updated to add the bug id

[Archie L. Cobbs]

8064931: tools/javac/scope/DupUnsharedTest.java needs to be updated to add the bug id

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Commit messages:
 - Add missing @bug tag to unit test.

Changes: https://git.openjdk.org/jdk/pull/10777/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10777&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8064931
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10777.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10777/head:pull/10777

PR: https://git.openjdk.org/jdk/pull/10777