Bump groovy in /net.tascalate.javaflow.tools.gradle

Bumps [groovy](https://github.com/apache/groovy) from 2.4.15 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] <[email protected]>

Author: dependabot[bot]

net.tascalate.javaflow.tools.gradle/pom.xml

@@ -50,7 +50,7 @@
 		<dependency>
 			<groupId>org.codehaus.groovy</groupId>
 			<artifactId>groovy</artifactId>
-			<version>2.4.15</version>
+			<version>2.4.21</version>
 			<scope>provided</scope>
 		</dependency>