chore(deps): update dependency com.google.cloud:libraries-bom to v21 (#376)

Author: renovate-bot

notification/snippets/pom.xml

@@ -28,7 +28,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>libraries-bom</artifactId>
-        <version>20.9.0</version>
+        <version>21.0.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>