remove securitymanager

[lukasj]

No description provided.

[darranl]

We haven't reached a point yet whereby we have an LTS release of Java where the security manager is disabled so at the moment all currently supported LTS versions of Java still support the activation of the security manager.

Additionally we still have a number of years until the last LTS release which supports the security manager goes out of support.

Looking at the root pom I believe this project is still trying to retain compatibility with Java 11, there are many enterprise installations out there on the older LTS releases and many still making use of the security manager - projects removing their security manager related code are inadvertently going to be creating regressions in these environments.