refactor code

Author: Larry Peterson

exercises.rst

@@ -81,8 +81,6 @@ Clone Repository
 
 To work on the exercises you will need to clone the following repo:
 
-.. code-block:: shell
-
 .. literalinclude:: code/clone.sh
 
 If the ``ngsdn-tutorial`` directory is already present in the VM, make
@@ -101,8 +99,6 @@ The VM may have shipped with an older version of the dependencies than
 you need for the exercises. You can upgrade to the latest version
 using the following command:
 
-.. code-block:: shell 
-
 .. literalinclude:: code/make.sh
 
 This command downloads all necessary Docker images (~1.5 GB), which