Bump junit from 4.12 to 4.13 (#6810)

Bumps [junit](https://github.com/junit-team/junit4) from 4.12 to 4.13.
- [Release notes](https://github.com/junit-team/junit4/releases)
- [Changelog](https://github.com/junit-team/junit4/blob/master/doc/ReleaseNotes4.12.md)
- [Commits](junit-team/junit4@r4.12...r4.13)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

build.gradle

@@ -4,7 +4,7 @@ buildscript {
   // ---------------------------------------
 
   ext.reactiveStreamsVersion = "1.0.3"
-  ext.junitVersion = "4.12"
+  ext.junitVersion = "4.13"
   ext.testNgVersion = "7.0.0"
   ext.mockitoVersion = "3.2.4"
   ext.jmhLibVersion = "1.21"