[Release 0.5.4] Update next snapshot version to 0.5.5-SNAPSHOT (#169)

Co-authored-by: onobc <onobc@apache.org>
diff --git a/gradle.properties b/gradle.properties
index 2a1f59c..b72100c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -17,4 +17,4 @@
 # under the License.
 #
 
-version=0.5.4
+version=0.5.5-SNAPSHOT