Fix formatting for bash commands

storage/storagedriver/device-mapper-driver.md

@@ -263,7 +263,7 @@ assumes that the Docker daemon is in the `stopped` state.
 7.  Convert the volumes to a thin pool and a storage location for metadata for
     the thin pool, using the `lvconvert` command.
 
-    ```none
+    ```bash
     $ sudo lvconvert -y \
     --zero n \
     -c 512K \