RFR: 7903397: Update changelog for jtreg 7.1.1

[Christian Stein]

Please review this commit that updates the changelog file to include a section for jtreg 7.1.1

It also adds the entry to the list of noteworthy unreleased changes of the upcoming jtreg 7.2 release.

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Commit messages:
 - 7903397: Update changelog for jtreg 7.1.1

Changes: https://git.openjdk.org/jtreg/pull/142/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=142&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903397
  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jtreg/pull/142.diff
  Fetch: git fetch https://git.openjdk.org/jtreg pull/142/head:pull/142

PR: https://git.openjdk.org/jtreg/pull/142