Provided an example on how to abandon a change

Added command line example to abandon a certain change.
The example was made to be as similar as possible to the previous
examples, reusing the same virtual SHA1.

Change-Id: I7f2ed88c59856d2a173aed3f8c3e84e4ec187b66
diff --git a/Documentation/cmd-review.txt b/Documentation/cmd-review.txt
index 4c87c26..f174034 100644
--- a/Documentation/cmd-review.txt
+++ b/Documentation/cmd-review.txt
@@ -106,6 +106,11 @@
     $(git rev-list origin/master..HEAD)
 ====
 
+Abandon an active change:
+====
+  $ ssh -p 29418 review.example.com gerrit review --abandon c0ff33
+====
+
 SEE ALSO
 --------