Integrated: 7903836: apidiff: Add GitHub Actions test workflow

[Christian Stein]

Please review this follow-up change to use the correct directory name for `workflows`.

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Commit messages:
 - Fix directory name

Changes: https://git.openjdk.org/apidiff/pull/11/files
  Webrev: https://webrevs.openjdk.org/?repo=apidiff&pr=11&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903836
  Stats: 0 lines in 1 file changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/apidiff/pull/11.diff
  Fetch: git fetch https://git.openjdk.org/apidiff.git pull/11/head:pull/11

PR: https://git.openjdk.org/apidiff/pull/11