feat(deps): adopt flatten plugin and google-cloud-shared-dependencies (#89)

Author: yangnuoyu

notification/snippets/pom.xml

@@ -23,14 +23,12 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>
 
-
-  <!-- [START notification_install_with_bom] -->
   <dependencyManagement>
     <dependencies>
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>libraries-bom</artifactId>
-        <version></version>
+        <version>7.0.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>
@@ -41,8 +39,9 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-notification</artifactId>
+      <!-- TODO: REMOVE VERSION SPECIFIED BELOW WHEN THE CLIENT GOES GA-->
+      <version>0.120.3-beta-SNAPSHOT</version>
     </dependency>
-    <!-- [END notification_install_with_bom] -->
 
     <dependency>
       <groupId>junit</groupId>