FMWK-638 add explicit mockito-core

[gagan405]

This is to suppress this and make it future proof :

Mockito is currently self-attaching to enable the inline-mock-maker. This will no longer work in future releases of the JDK. Please add Mockito as an agent to your build as described in Mockito's documentation: https://javadoc.io/doc/org.mockito/mockito-core/latest/org.mockito/org/mockito/Mockito.html#0.3
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
WARNING: A Java agent has been loaded dynamically (/Users/gmishra/.m2/repository/net/bytebuddy/byte-buddy-agent/1.15.11/byte-buddy-agent-1.15.11.jar)
WARNING: If a serviceability tool is in use, please run with -XX:+EnableDynamicAgentLoading to hide this warning
WARNING: If a serviceability tool is not in use, please run with -Djdk.instrument.traceUsage for more information
WARNING: Dynamic loading of agents will be disallowed by default in a future release

[agrgr]

Overall looks good. Please choose a label (in this case likely "enhancement"). Reviewer and label are required for every PR.