Docs 15375 (#1176)

* DOCS-15375: Fix TLS cert name

* DOCS-15375: Minor edits

* DOCS-15375: Minor edit

Co-authored-by: Sarah Olson <[email protected]>

Author: sarah-olson-mongodb

source/tutorial/upgrade-cluster-to-ssl.txt

@@ -76,7 +76,7 @@ process.
                 net:
                    tls:
                       mode: allowTLS
-                      PEMKeyFile: <path to TLS/SSL certificate and key PEM file>
+                      certificateKeyFile: <path to TLS/SSL certificate and key PEM file>
                       CAFile: <path to root CA PEM file>
 
    Upgrade all nodes of the cluster to these settings.
@@ -176,7 +176,7 @@ process.
                 net:
                    ssl:
                       mode: <allowSSL>
-                      PEMKeyFile: <path to TLS/SSL certificate and key PEM file>
+                      certificateKeyFile: <path to TLS/SSL certificate and key PEM file>
                       CAFile: <path to root CA PEM file>
 
    Upgrade all nodes of the cluster to these settings.