Update version number to 0.4.0 (#8204)

Author: busunkim96

dataproc/setup.py

@@ -22,7 +22,7 @@
 
 name = "google-cloud-dataproc"
 description = "Google Cloud Dataproc API client library"
-version = "0.3.1"
+version = "0.4.0"
 # Should be one of:
 # 'Development Status :: 3 - Alpha'
 # 'Development Status :: 4 - Beta'