Doc review: remove mention of Avocado in the Configuration section title

This is obviously about Avocado, and just having "Configuration" makes it
easier on the brain and on the eyes.
Signed-off-by: NCleber Rosa <crosa@redhat.com>

docs/source/Configuration.rst

-=====================
-Avocado Configuration
-=====================
+===============
+ Configuration
+===============
 
 Avocado utilities have a certain default behavior based on educated, reasonable (we hope) guesses about how
 users like to use their systems. Of course, different people will have different needs and/or dislike our defaults,