fix: incremented versions for jackson and netty

[akafredperry]

#closes 379

- What I did
Updated versions of 3rd party jars (jackson & netty)

- How I did it
Modified properties in parent pom

- How to verify it
Run a clean mvn install which will run all the unit and integration tests
Create a new intellij java project and add a dependency for

    <dependency>
      <groupId>org.atsign</groupId>
      <artifactId>at_client</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>

No vulnerabilities should be reported

- Description for the changelog

fix: upgrade dependencies for jackson to 2.21.1 and netty to 4.2.12.Final