Bump groovy from 2.1.9 to 2.4.21 in /extensions/groovy

Bumps [groovy](https://github.com/apache/groovy) from 2.1.9 to 2.4.21.
- [Release notes](https://github.com/apache/groovy/releases)
- [Commits](https://github.com/apache/groovy/commits)

---
updated-dependencies:
- dependency-name: org.codehaus.groovy:groovy
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/extensions/groovy/pom.xml b/extensions/groovy/pom.xml
index 94a3a56..39f0cc3 100644
--- a/extensions/groovy/pom.xml
+++ b/extensions/groovy/pom.xml
@@ -31,7 +31,7 @@
         <dependency>
             <groupId>org.codehaus.groovy</groupId>
             <artifactId>groovy</artifactId>
-            <version>2.1.9</version>
+            <version>2.4.21</version>
         </dependency>
     </dependencies>
 </project>