docsite/rst/intro_configuration.rst: reword Title.

Make Configuration the first word, so that it is in line with other documents
and that system administrators/devops people don't lose the tab when having
many browser tabs open.

docsite/rst/intro_configuration.rst

-The Ansible Configuration File
-++++++++++++++++++++++++++++++
+Configuration file
+++++++++++++++++++
 
 .. contents:: Topics