DOCSP-23994 fix Invalid ubuntu image version (#993)

* DOCSP-23994 fix Invalid ubuntu image version

* DOCSP-23994 updates for CR feedback

Author: kanchana-mongodb

source/includes/steps-deploy-k8s-opsmgr-local-mode.yaml

@@ -270,7 +270,7 @@ content: |
      .. tab:: Vanilla Kubernetes
         :tabid: k8s
 
-        a. Download the Ubuntu 16.04 installation tarball for the
+        a. Download the Ubuntu 20.04 installation tarball for the
            MongoDB Server version you want the |k8s-op-short| to
            deploy. For example, to download the ``4.4.0`` release:
 
@@ -280,7 +280,7 @@ content: |
 
         #. If you deployed a version of |onprem| from 4.4.0 up to and
            including 4.4.3, you must also
-           download the Ubuntu 16.04 MongoDB Database Tools installation
+           download the Ubuntu 20.04 MongoDB Database Tools installation
            tarball. For example, to download the ``{+mdbtools-version+}`` release:
 
            .. code-block:: sh

source/tutorial/plan-k8s-op-container-images.txt

@@ -78,6 +78,6 @@ a container registry:
 
 .. note::
 
-   Images from Quay.io use Ubuntu 16.04 by default. Append 
+   Images from Quay.io use Ubuntu 20.04 by default. Append 
    ``-ubi`` to an image name to retrieve a version that uses 
    Red Hat UBI 8.