doc: Fix a grammar error in rbd-snapshot.rst

Signed-off-by: Zeqing Tyler Qi <aqize@126.com>

diff --git a/doc/rbd/rbd-snapshot.rst b/doc/rbd/rbd-snapshot.rst
index 547f483f7331cea544a15e5e0c4315df315ef0ff..1cb6cb309ccc44fc3c247efe3d30b8be9c0dbe20 100644 (file)
--- a/doc/rbd/rbd-snapshot.rst
+++ b/doc/rbd/rbd-snapshot.rst
@@ -202,7 +202,7 @@ clone snapshots  from one pool to images in another pool.
 
 
 #. **Image Template:** A common use case for block device layering is to create a
-   a master image and a snapshot that serves as a template for clones. For example, 
+   master image and a snapshot that serves as a template for clones. For example, 
    a user may create an image for a Linux distribution (e.g., Ubuntu 12.04), and 
    create a snapshot for it. Periodically, the user may update the image and create
    a new snapshot (e.g., ``sudo apt-get update``, ``sudo apt-get upgrade``,