Bump version on GROOVY_4_0_X branch

Author: paulk-asert

gradle.properties

@@ -13,9 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-groovyVersion=4.0.19-SNAPSHOT
+groovyVersion=4.0.20-SNAPSHOT
 # bundle version format: major('.'minor('.'micro('.'qualifier)?)?)? (first 3 only digits)
-groovyBundleVersion=4.0.19.SNAPSHOT
+groovyBundleVersion=4.0.20.SNAPSHOT
 
 groovyTargetBytecodeVersion=1.8
 targetJavaVersion=8