Upgrade to Spring Cloud GCP 7.3.0 and 6.3.3

See gh-1895

Signed-off-by: Lawrence Qiu <[email protected]>

Author: lqiu96

start-site/src/main/resources/application.yml

@@ -113,9 +113,9 @@ initializr:
         additionalBoms: [ spring-cloud ]
         mappings:
           - compatibilityRange: "[3.4.0,3.5.0-M1)"
-            version: 6.3.0
+            version: 6.3.3
           - compatibilityRange: "[3.5.0,4.0.0-M1)"
-            version: 7.1.0
+            version: 7.3.0
       spring-cloud-services:
         groupId: io.pivotal.spring.cloud
         artifactId: spring-cloud-services-dependencies