Update the project version to 0.84.1-SNAPSHOT

Author: armerian

gradle.properties

@@ -1,5 +1,5 @@
 group=com.linecorp.centraldogma
-version=0.83.1-SNAPSHOT
+version=0.84.1-SNAPSHOT
 projectName=Central Dogma
 projectUrl=https://line.github.io/centraldogma/
 projectDescription=Highly-available version-controlled service configuration repository based on Git, ZooKeeper and HTTP/2