DOCS-4896 - Fix incorrect compatibility version for PyMongo

Author: Michael Paik

source/release-notes/3.0-compatibility.txt

@@ -446,7 +446,7 @@ The minimum 3.0-compatible driver versions are:
      - `1.5 <http://pecl.php.net/package/mongo>`_
 
    * - :ecosystem:`Python </drivers/python>`
-     - `3.0 <https://pypi.python.org/pypi/pymongo/>`_
+     - `2.8 <https://pypi.python.org/pypi/pymongo/>`_
 
    * - :ecosystem:`Motor </drivers/python>`
      - `0.4 <https://pypi.python.org/pypi/motor/>`_