fix(deps): update dependency com.google.auth:google-auth-library-bom to v1.15.0 (#1278)

Author: renovate-bot

gapic-generator-java-pom-parent/pom.xml

@@ -26,8 +26,8 @@
     <!-- External dependencies, expecially gRPC and Protobuf version, should be
         consistent across modules in this repository -->
     <javax.annotation-api.version>1.3.2</javax.annotation-api.version>
-    <grpc.version>1.53.0</grpc.version>
-    <google.auth.version>1.16.0</google.auth.version>
+    <grpc.version>1.52.1</grpc.version>
+    <google.auth.version>1.15.0</google.auth.version>
     <gson.version>2.10.1</gson.version>
     <guava.version>31.1-jre</guava.version>
     <protobuf.version>3.21.12</protobuf.version>