chore: add property tag for shared-deps (#565)

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Fixes #<issue_number_goes_here> ☕️

pom.xml

@@ -63,14 +63,15 @@
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
     <github.global.server>github</github.global.server>
     <site.installationModule>google-cloud-storage-parent</site.installationModule>
+    <google.cloud.shared-dependencies.version>0.10.2</google.cloud.shared-dependencies.version>
   </properties>
 
   <dependencyManagement>
     <dependencies>
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-shared-dependencies</artifactId>
-        <version>0.10.2</version>
+        <version>${google.cloud.shared-dependencies.version}</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>