RFR: 8173: 2023-12 target platform needs update to take org.eclipse.ui.themes

[Virag Purnam]

2023-12 target platform needs update to take org.eclipse.ui.themes.
org.eclipse.ui.themes has been added as part for Dark Mode Fix. Build on master has failed because of this.

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Commit messages:
 - 8173: 2023-12 target platform needs update to take org.eclipse.ui.themes

Changes: https://git.openjdk.org/jmc/pull/550/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=550&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8173
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jmc/pull/550.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/550/head:pull/550

PR: https://git.openjdk.org/jmc/pull/550