Bump mysql-connector-java from 8.0.20 to 8.0.21 in /modules/junit-jupiter (#3037)

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.20 to 8.0.21.
- [Release notes](https://github.com/mysql/mysql-connector-j/releases)
- [Changelog](https://github.com/mysql/mysql-connector-j/blob/release/8.0/CHANGES)
- [Commits](mysql/mysql-connector-j@8.0.20...8.0.21)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Richard North <[email protected]>

Author: dependabot[bot]

modules/junit-jupiter/build.gradle

@@ -16,7 +16,7 @@ dependencies {
     testCompile 'org.junit.jupiter:junit-jupiter-params:5.6.2'
 
     testRuntime 'org.postgresql:postgresql:42.2.14'
-    testRuntime 'mysql:mysql-connector-java:8.0.20'
+    testRuntime 'mysql:mysql-connector-java:8.0.21'
     testRuntime 'org.junit.jupiter:junit-jupiter-engine:5.6.2'
 }