Bump com.squareup.okio:okio from 3.11.0 to 3.15.0

Bumps [com.squareup.okio:okio](https://github.com/square/okio) from 3.11.0 to 3.15.0.
- [Release notes](https://github.com/square/okio/releases)
- [Changelog](https://github.com/square/okio/blob/master/CHANGELOG.md)
- [Commits](square/okio@parent-3.11.0...parent-3.15.0)

---
updated-dependencies:
- dependency-name: com.squareup.okio:okio
  dependency-version: 3.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

agent/agent-tooling/build.gradle.kts

@@ -63,7 +63,7 @@ dependencies {
   testImplementation("io.opentelemetry:opentelemetry-sdk-testing")
 
   // TODO(trask): update tests, no need to use this anymore
-  testImplementation("com.squareup.okio:okio:3.11.0")
+  testImplementation("com.squareup.okio:okio:3.15.0")
 
   compileOnly(project(":agent:agent-bootstrap"))
   compileOnly("io.opentelemetry.instrumentation:opentelemetry-instrumentation-api")