DOCS-15747 Update PyMongo Installation Instructions (#846)

* update pymongo installation page

* CC review comment edits

* style guide edits

Author: ajhuh-mdb

source/pymongo.txt

@@ -42,27 +42,32 @@ You must install the PyMongo driver module to make it available to your
 Python application. We recommend using
 `pip <http://pypi.python.org/pypi/pip>`__ to install PyMongo.
 
+PyMongo requires `dnspython <https://pypi.org/project/dnspython>`__  to support 
+``mongodb+srv://`` connection strings and `MongoDB Atlas 
+<https://www.mongodb.com/cloud>`__. ``dnspython`` is automatically installed 
+when installing or upgrading to the latest PyMongo version. 
+
 The following command demonstrates how you can install the latest
 version of the module using the command line:
 
 .. code-block:: sh
 
-   $ python -m pip install 'pymongo[srv]'
+   $ python -m pip install pymongo
 
-If you need to install a specific version of ``pymongo``, specify the
+If you need to install a specific version of PyMongo, specify the
 version in your command. The following command shows how you can use
 ``pip`` to install PyMongo version ``3.11``:
 
 .. code-block:: sh
 
-   $ python -m pip install 'pymongo[srv]'==3.11
+   $ python -m pip install pymongo==3.11
 
 If you already have PyMongo installed and need to upgrade to the latest
 version, use the following ``pip`` command:
 
 .. code-block:: sh
 
-   $ python -m pip install --upgrade 'pymongo[srv]'
+   $ python -m pip install --upgrade pymongo
 
 See `Installation <https://pymongo.readthedocs.io/en/stable/installation.html>`__
 for more ways to install PyMongo.