chore(release): format version qualifier with SemVer hyphen delimiter (#27)

- Change version from '0.4.0rc1' to '0.4.0-rc1' in
  data-manager-util/build.gradle.
- Align release candidate version formatting with Semantic Versioning
  2.0.0 and Maven version comparator expectations.

Author: jradcliff

data-manager-util/build.gradle

@@ -28,7 +28,7 @@ if (isPublishing) {
 
 group = 'com.google.api-ads'
 description = 'Utilities for working with the Data Manager API'
-version = '0.4.0rc1'
+version = '0.4.0-rc1'
 
 java {
     sourceCompatibility = JavaVersion.VERSION_1_8