Bump junit from 4.12 to 4.13

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/main/doc/ReleaseNotes4.12.md)
- [Commits](junit-team/junit4@r4.12...r4.13)

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

Author: dependabot[bot]

build.gradle

@@ -31,7 +31,7 @@ dependencies {
     implementation 'com.google.guava:guava:20.0'
 
     // Use JUnit test framework
-    testImplementation 'junit:junit:4.12'
+    testImplementation 'junit:junit:4.13'
 
     api 'com.squareup.okhttp3:okhttp:3.12.1'