[ci] Skip slack for retries JDK matrix jobs

[dliappis]

Release notes

[rn:skip]

What does this PR do?

With this commit we shush slack alerts for JDK matrix CI jobs that succeed after (automatic) retries.

Why is it important/What is the impact to the user?

Reduces notification fatigue for non-actionable events.

[elastic-sonarqube[bot]]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

:green_heart: Build Succeeded

• Buildkite Build
• Commit: 4e970ac7c3b83f7813415573999915b5a2e445a0

cc @dliappis