remove references to EOL server versions (#260)

(cherry picked from commit 78d1807)

Author: jordan-smith721

source/includes/list-prerequisites.rst

@@ -4,7 +4,7 @@
   `MongoDB white paper <https://www.mongodb.com/collateral/apache-spark-and-mongodb-turning-analytics-into-real-time-action>`__
   for more details.
 
-- MongoDB version 4.0 or later
+- MongoDB version 6.0 or later
 
 - Spark version 3.1 through 3.5
 

source/index.txt

@@ -55,4 +55,4 @@ versions of Apache Spark and MongoDB:
 
    * - **{+current-version+}**
      - **3.1 through 3.5**
-     - **4.0 or later**
+     - **6.0 or later**