docs: remove static modules.png file and its reference in the docs

The modules.png file is a static file that would need manual update
with almost every single commit. This is rather impractical and
doesn't add that much value to the regular user.

If a developer wants to take a look at the dependency graph, a
Makefile target still exists that will give a user a fresh graph.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

docs/source/DevelopmentTips.rst

@@ -150,7 +150,3 @@ My usual workflow is:
 
 This way you always have all the files present and you can easily resume
 your work.
-
-Module Dependencies
-===================
-.. figure:: modules.png