refactor: remove unused test method

[yeikel]

As far as I can tell, this method is not used

As a bonus, we stop using the deprecated X509Certificate class

[vietj]

this might be used in other project depending on vertx core so a check on those project should be done

[yeikel]

this might be used in other project depending on vertx core so a check on those project should be done

What other projects are you referring to? Where should I check?

[vietj]

other projects in vert-x3 or eclipse-vertx, some of them rely on vertx-core test artifact

[yeikel]

other projects in vert-x3 or eclipse-vertx, some of them rely on vertx-core test artifact

I am a bit confused here because this is coming from a test class and test classes are typically not published for others to use

I searched for this method name, and all the usages are from within this same project (and the method with the other signature)

[vietj]

that might be confusing but you can look at vertx-web and how it uses vertx-core VertxTest for instance