doc: Remove Python prompt tutorial snippet

Reasons are:

- The prompt says 2.7.3  Sep 26 2013, which makes the tutorial look
  outdated
- There is another section that explains how snippets should be
  executed in a Python interactive interpreter
- The only activity in the snippet is importing tuf functions and
  creating a repo, both of which is done in another snippet below.
  And the here created repo is not re-used
- The tutorial is long enough

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>

docs/TUTORIAL.md

@@ -38,17 +38,7 @@ updates](../tuf/ATTACKS.md).
 The [repository tool](../tuf/repository_tool.py) contains functions to generate
 all of the files needed to populate and manage a TUF repository.  The tool may
 either be imported into a Python module, or used with the Python interpreter in
-interactive mode.  For instance, here is an example of initializing a TUF
-repository in interactive mode:
-
-```Bash
-$ python
-Python 2.7.3 (default, Sep 26 2013, 20:08:41)
-[GCC 4.6.3] on linux2
-Type "help", "copyright", "credits" or "license" for more information.
->>> from tuf.repository_tool import *
->>> repo = create_new_repository("my_repo")
-```
+interactive mode.
 
 A repository object that encapsulates the metadata files of the repository can
 be created or loaded by the repository tool.  Repository maintainers can modify