Remove dependency on jcenter

[artursouza]

Expected Behavior

JCenter is being shut down, so we should depend on another public mirror: https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/

Actual Behavior

SDk build depends on a public mirror reaching end of life.

Steps to Reproduce the Problem

See notice: https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/

Release Note

RELEASE NOTE: MIGRATED out of JCenter as a Maven repository.

[mthmulders]

What exactly do we use JCenter for? I believe all released versions of the Dapr SDK for Java are already published to Maven Central...

[artursouza]

It is where we are downloading our dependencies from.

[mthmulders]

/assign

[mthmulders]

There was one artifact (com.github.gmazzo:okhttp-mock:1.3.2) that wasn't deployed to Maven Central, only to JCenter. I've upgraded that one to the latest version (1.4.1) which is available in Maven Central.