Fix dead links

Not sure if the updated links are the ones you intended, but that's the location of each of these files...

Author: lukaseder

docs/usage/database_containers.md

@@ -40,8 +40,8 @@ Note that if you use `@Rule`, you will be given an isolated container for each t
 
 Examples/Tests:
 
- * [MySQL](https://github.com/testcontainers/testcontainers-java/blob/master/modules/mysql/src/test/java/org/testcontainers/junit/SimpleMySQLTest.java)
- * [PostgreSQL](https://github.com/testcontainers/testcontainers-java/blob/master/modules/postgresql/src/test/java/org/testcontainers/junit/SimplePostgreSQLTest.java)
+ * [MySQL](https://github.com/testcontainers/testcontainers-java/blob/master/modules/jdbc-test/src/test/java/org/testcontainers/junit/SimpleMySQLTest.java)
+ * [PostgreSQL](https://github.com/testcontainers/testcontainers-java/blob/master/modules/jdbc-test/src/test/java/org/testcontainers/junit/SimplePostgreSQLTest.java)
  * [Oracle-XE](https://github.com/testcontainers/testcontainers-java/blob/master/modules/oracle-xe/src/test/java/org/testcontainers/junit/SimpleOracleTest.java)
  * [Virtuoso](https://github.com/testcontainers/testcontainers-java/blob/master/modules/virtuoso/src/test/java/org/testcontainers/junit/SimpleVirtuosoTest.java)