Bump step-security/harden-runner from 2.14.2 to 2.15.0

Bump step-security/harden-runner from 2.14.2 to 2.15.0

## Release notes

Sourced from step-security/harden-runner's releases.

v2.15.0
What's Changed
Windows and macOS runner support
We are excited to announce that Harden Runner now supports Windows and macOS runners, extending runtime security beyond Linux for the first time.
Insights for Windows and macOS runners will be displayed in the same consistent format you are already familiar with from Linux runners, giving you a unified view of runtime activity across all platforms.
Full Changelog: https://github.com/step-security/harden-runner/compare/v2.14.2...v2.15.0

## Commits

a90bcbc Update readme (#637)
f0a59d8 Release v2.15.0 (#639)
See full diff in compare view

![Dependabot compatibility score](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores)

Issue-ID: CIMAN-33
Signed-off-by: dependabot[bot] <support@github.com>
Change-Id: I5789e78bb5d46386cf651d7be87707d07e99acf9
GitHub-PR: https://github.com/onap/doc/pull/6
GitHub-Hash: dc3c7d2d2af98a26
Signed-off-by: onap.gh2gerrit <releng+onap-gh2gerrit@linuxfoundation.org>