build(deps): update dependency com.google.cloud:google-cloud-shared-config to v1.15.1

Author: renovate[bot]

pom.xml

@@ -14,7 +14,7 @@
   <parent>
     <groupId>com.google.cloud</groupId>
     <artifactId>google-cloud-shared-config</artifactId>
-    <version>1.5.3</version>
+    <version>1.15.1</version>
   </parent>
 
   <developers>