(DOCSP-39052) Remove downgrading to 4.0 as links have been broken due to earlier removal of actual steps (#181)

Remove downgrading files and tab for 4.0 due to previously removed steps.

Author: JuliaMongo

source/includes/considerations-change-mongodb-version.rst

@@ -25,7 +25,3 @@
 
    - From version 5.0 to any version before 4.4.0
    - From version 4.4 to any version before 4.2.6
-   - From version 4.2 to any version 4.0.12 (for Windows) or 4.0.7 
-     (for Linux)
-   - From version 4.0 to any version before 3.6.23
-

source/includes/steps-remove-incompat-features-42-40.yaml

@@ -60,12 +60,6 @@ manually downgrade the instance's :manual:`featureCompatibilityVersion</referenc
 
       .. include:: /includes/steps/remove-incompat-features-44-42.rst
 
-   .. tab:: 4.2 to 4.0
-      :tabid: four-two-to-four-oh
-
-      .. include:: /includes/steps/remove-incompat-features-42-40.rst
-
-
 Procedure
 ---------