Update IDEA requirements to 2018.3.6

> Access to unresolved class RunConfigurationSingletonPolicy (1 problem)
Method EmptyRunConfigurationFactory.getSingletonPolicy() references an unresolved class RunConfigurationSingletonPolicy. This can lead to NoSuchClassError exception at runtime.

Regarding the plugin verifier it is 100% compatible since IntelliJ IDEA Ultimate IU-183.6156.11 (2018.3.6)