Update the docs for deploying subprojects in Google Cloud Storage

Deploying usually worked because each maintainer already had the
gs-maven-wagon in his local maven repository. However, once the local
maven repository was wiped the deploying didn't work because the
gs-maven-wagon was not available in the maven central.

Adding the google storage as a pluginRepository solves the issue
because gs-maven-wagon can be downloaded from there.

Change-Id: Ia4965ed7138d4d937f567fb10f0074f08e1af8cb

Documentation/dev-release-deploy-config.txt

diff --git a/Documentation/dev-release-deploy-config.txt b/Documentation/dev-release-deploy-config.txt
index b2c5358..fe17967 100644
--- a/Documentation/dev-release-deploy-config.txt
+++ b/Documentation/dev-release-deploy-config.txt
@@ -143,7 +143,14 @@
 ----
 
 
-* Add this to the `pom.xml` to enable the wagon provider:
+* Add these two snippets to the `pom.xml` to enable the wagon provider:
+
+----
+  <pluginRepository>
+    <id>google-storage</id>
+    <url>https://console.developers.google.com/storage/browser/gerrit-maven/</url>
+  </pluginRepository>
+----
 
 ----
   <build>