Bump mysql-connector-java from 8.0.15 to 8.0.16 in /modules/spock (testcontainers#1429)

Bumps [mysql-connector-java](https://github.com/mysql/mysql-connector-j) from 8.0.15 to 8.0.16.
- [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@8.0.15...8.0.16)

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

Author: dependabot[bot]

modules/spock/build.gradle

@@ -14,5 +14,5 @@ dependencies {
     testCompile 'org.apache.httpcomponents:httpclient:4.5.8'
 
     testRuntime 'org.postgresql:postgresql:42.2.5'
-    testRuntime 'mysql:mysql-connector-java:8.0.15'
+    testRuntime 'mysql:mysql-connector-java:8.0.16'
 }