Bump org.assertj:assertj-core in /data-prepper-plugins/otel-trace-source

Bumps [org.assertj:assertj-core](https://github.com/assertj/assertj) from 3.25.3 to 3.26.3.
- [Release notes](https://github.com/assertj/assertj/releases)
- [Commits](assertj/assertj@assertj-build-3.25.3...assertj-build-3.26.3)

---
updated-dependencies:
- dependency-name: org.assertj:assertj-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

data-prepper-plugins/otel-trace-source/build.gradle

@@ -28,7 +28,7 @@ dependencies {
     implementation libs.commons.lang3
     implementation libs.bouncycastle.bcprov
     implementation libs.bouncycastle.bcpkix
-    testImplementation 'org.assertj:assertj-core:3.25.3'
+    testImplementation 'org.assertj:assertj-core:3.26.3'
     testImplementation testLibs.slf4j.simple
     testImplementation libs.commons.io
 }