doc: Fix copy-paste error in Docker section of Python API scanning

doc/manual/source/python.rst

@@ -563,20 +563,21 @@ As a prerequisite, install Docker using a package manager; on Ubuntu, use:
 
     $ apt install docker.io
 
-To allow an unprivileged user to use Docker, perform the following
+To allow an unprivileged user to use Docker, perform the following:
 
 .. sourcecode:: bash
 
-    $ apt install docker.io
+    $ sudo chmod 666 /var/run/docker.sock
 
-Then execute the following steps to get a shell:
+The following command will obtain a raw shell for an Ubuntu 20.04 image: 
 
 .. sourcecode:: bash
     
     $ docker run -it ubuntu:20.04
 
-If you prefer to work on your current directory from the container shell,
-instead do:
+However, if you prefer to work on your current directory from the container
+shell, use the ``-v`` option to request a bind mount of a host directory
+to a container directory, such as follows:
 
 .. sourcecode:: bash
 
@@ -600,6 +601,9 @@ steps to rescan the APIs and test them:
     $ ./ns3 build
     $ ./ns3 run ./utils/python-unit-tests.py
 
+If you only want to scan one module, specify ``MODULENAME-apiscan``
+(such as ``wifi-apiscan``) instead of ``apiscan-all`` in the above.
+
 If you exit the container, the package state will be lost, but from another
 terminal window, you may be able to further test and evaluate the new bindings.
 Note that the new bindings and build files will have root file ownership.