Remove long-deprecated unused encoding property from VerifyMojo

[Tomlincoln]

Since 2.20.1 this is deprecated, but as far as I cheked this encoding property in VerifyMojo is not used anywhere.
It's a minor iconvenience to see a warning about it in every build log.

• [ x ] Each commit in the pull request should have a meaningful subject line and body.

• [ x ] Write a pull request description that is detailed enough to understand what the pull request does, how, and why.

• [ x ] Run mvn clean install to make sure basic checks pass. A more thorough check will
  be performed on your pull request automatically.

• [ x ] You have run the integration tests successfully (mvn -Prun-its clean install).

• [ x ] I hereby declare this contribution to be licenced under the Apache License Version 2.0, January 2004

[Tomlincoln]

@slachiewicz Is there anything I can help you with regarding this PR ?

[olamy]

not sure to understand if you are not using this property in your pom you should not see this warning.
so the warning means you are still using it in your pom.
Simply remove it from your pom and you will not have the warning anymore