Add dependency to kotlin.jar to gradle file

[fmagin]

This allows gradle prepDev of a Ghidra development setup to pickup the dependency on the jar and add it to the build/libraryDependencies.txt which is used to collect the external jars in development mode. Relevant code is https://github.com/NationalSecurityAgency/ghidra/blob/855955bb3de853b165fd292468c40e20e179ecb1/Ghidra/Framework/Utility/src/main/java/ghidra/GhidraLauncher.java#L59-L66