Update to Groovy 2.4.21

Closes gh-9605

gradle/dependency-management.gradle

@@ -158,9 +158,9 @@ dependencyManagement {
 		dependency 'org.attoparser:attoparser:2.0.4.RELEASE'
 		dependency 'org.bouncycastle:bcpkix-jdk15on:1.64'
 		dependency 'org.bouncycastle:bcprov-jdk15on:1.64'
-		dependency 'org.codehaus.groovy:groovy-all:2.4.20'
-		dependency 'org.codehaus.groovy:groovy-json:2.4.20'
-		dependency 'org.codehaus.groovy:groovy:2.4.20'
+		dependency 'org.codehaus.groovy:groovy-all:2.4.21'
+		dependency 'org.codehaus.groovy:groovy-json:2.4.21'
+		dependency 'org.codehaus.groovy:groovy:2.4.21'
 		dependency 'org.eclipse.jdt:ecj:3.12.3'
 		dependency 'org.eclipse.jetty.websocket:websocket-api:9.4.36.v20210114'
 		dependency 'org.eclipse.jetty.websocket:websocket-client:9.4.36.v20210114'