Bump workflow-aggregator from 2.5 to 2.6

Bumps workflow-aggregator from 2.5 to 2.6.

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

Author: dependabot[bot]

pom.xml

@@ -120,7 +120,7 @@
     <dependency>
       <groupId>org.jenkins-ci.plugins.workflow</groupId>
       <artifactId>workflow-aggregator</artifactId>
-      <version>2.5</version>
+      <version>2.6</version>
       <scope>test</scope>
     </dependency>
     <dependency>