Release 6.0.2-lts: Bumping to next version post release (#2386)

* preparing release 6.0.2-lts

* 6.0.3-SNAPSHOT

Author: zhumin8

boms/cloud-lts-bom/pom.xml

@@ -7,7 +7,7 @@
 
   <groupId>com.google.cloud</groupId>
   <artifactId>gcp-lts-bom</artifactId>
-  <version>6.0.2-SNAPSHOT</version>
+  <version>6.0.3-SNAPSHOT</version>
   <packaging>pom</packaging>
 
   <name>Google Cloud Long Term Support BOM</name>