Bump pulsar-client-admin from 2.5.1 to 2.6.0 in /modules/pulsar (#2975)

Bumps [pulsar-client-admin](https://github.com/apache/pulsar) from 2.5.1 to 2.6.0.
- [Release notes](https://github.com/apache/pulsar/releases)
- [Commits](apache/pulsar@v2.5.1...v2.6.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

modules/pulsar/build.gradle

@@ -5,5 +5,5 @@ dependencies {
 
     testCompile group: 'org.apache.pulsar', name: 'pulsar-client', version: '2.6.0'
     testCompile group: 'org.assertj', name: 'assertj-core', version: '3.16.1'
-    testCompile group: 'org.apache.pulsar', name: 'pulsar-client-admin', version: '2.5.1'
+    testCompile group: 'org.apache.pulsar', name: 'pulsar-client-admin', version: '2.6.0'
 }