RFR: 8318448: Link PopupMenu/PopupMenuLocation.java failure to JDK-8259913

[Alexey Ivanov]

Update ProblemList entry for java/awt/PopupMenu/PopupMenuLocation.java to [JDK-8259913](https://bugs.openjdk.org/browse/JDK-8259913) which is a specific bug for AWT menus in High DPI environment.

-------------

Commit messages:
 - 8318448: Link PopupMenu/PopupMenuLocation.java failure to JDK-8259913

Changes: https://git.openjdk.org/jdk/pull/16246/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16246&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318448
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16246.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16246/head:pull/16246

PR: https://git.openjdk.org/jdk/pull/16246