sweep: #7309 docs minor updates

Author: fstagni

docs/source/AdministratorGuide/index.rst

@@ -7,7 +7,7 @@ Administrator Guide
 DIRAC has been developed with extensibility and flexibility in mind. A DIRAC release is composed by few projects, like in the following picture.
 This administration documentation refers to the "Core" DIRAC project.
 
-.. image:: ../_static/horizontalAndVertical-ext.png
+.. image:: ../_static/py3Stack.png
    :alt: DIRAC projects interaction overview
    :align: center
 

docs/source/UserGuide/GettingStarted/InstallingClient/index.rst

@@ -21,9 +21,9 @@ So, you first install DIRACOS2 and only then install DIRAC in it::
 
 and now DIRAC::
 
-  $ pip install DIRAC==8.0
+  $ pip install DIRAC
 
-(Just `pip install DIRAC` will install the most recent production version found on https://pypi.org/project/DIRAC/)
+will install the most recent production version found on https://pypi.org/project/DIRAC/
 
 And for the configuration::