RFR: 7903719: Release jtreg 7.4

[Christian Stein]

Please review this change preparing the release of `jtreg` 7.4

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Commit messages:
 - 7903719: Release jtreg 7.4

Changes: https://git.openjdk.org/jtreg/pull/193/files
  Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=193&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903719
  Stats: 10 lines in 2 files changed: 8 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jtreg/pull/193.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/193/head:pull/193

PR: https://git.openjdk.org/jtreg/pull/193