RFR: CODETOOLS-7903287: Remove left-over obsolete support for Ant task

[Jonathan Gibbons]

Please review a trivial update to remove some dead code left over from when the Ant task was removed earlier this year.

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Commit messages:
 - CODETOOLS-7903287: Remove left-over obsolete support for Ant task

Changes: https://git.openjdk.org/jtreg/pull/111/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=111&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903287
  Stats: 8 lines in 1 file changed: 0 ins; 8 del; 0 mod
  Patch: https://git.openjdk.org/jtreg/pull/111.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/111/head:pull/111

PR: https://git.openjdk.org/jtreg/pull/111