build.gradle: Add 'testRuntime' configuration to artifacts
build.gradle: Add 'testRuntime' configuration to artifacts

To complete the 'testRuntime' artifact configuration.

vanitasvitae/smack-omemo,esl/Smack,Flowdalic/Smack,annovanvliet/Smack,esl/Smack,igniterealtime/Smack,Flowdalic/Smack,vanitasvitae/Smack,vanitasvitae/smack-omemo,Flowdalic/Smack,esl/Smack,vanitasvitae/Smack,annovanvliet/Smack,vanitasvitae/smack-omemo,vanitasvitae/Smack,annovanvliet/Smack,igniterealtime/Smack,igniterealtime/Smack