Bump net.bytebuddy:byte-buddy-agent in /data-prepper-plugins/opensearch

Bumps [net.bytebuddy:byte-buddy-agent](https://github.com/raphw/byte-buddy) from 1.14.17 to 1.15.7.
- [Release notes](https://github.com/raphw/byte-buddy/releases)
- [Changelog](https://github.com/raphw/byte-buddy/blob/master/release-notes.md)
- [Commits](raphw/byte-buddy@byte-buddy-1.14.17...byte-buddy-1.15.7)

---
updated-dependencies:
- dependency-name: net.bytebuddy:byte-buddy-agent
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

data-prepper-plugins/opensearch/build.gradle

@@ -42,7 +42,7 @@ dependencies {
     testImplementation testLibs.junit.vintage
     testImplementation libs.commons.io
     testImplementation 'net.bytebuddy:byte-buddy:1.14.17'
-    testImplementation 'net.bytebuddy:byte-buddy-agent:1.14.17'
+    testImplementation 'net.bytebuddy:byte-buddy-agent:1.15.7'
     testImplementation testLibs.slf4j.simple
 }