DOCS-11297: macos tarball instruction

Author: kay-kim

source/includes/steps-install-mongodb-on-osx-manually.yaml

@@ -1,15 +1,10 @@
 stepnum: 1
 level: 4
-source:
-  file: steps-install-mongodb-on-linux.yaml
-  ref: download
-# The content of the following include is autogenerated:
-action:
-  pre: |
-    For example, to download the latest release through the shell, issue
-    the following:
-
-    .. include:: /includes/release/curl-release-osx-x86_64.rst
+title: Download the MongoDB .tgz file.
+ref: download
+pre: |
+  Download the tarball for macOS from the `MongoDB Download Center
+  <https://www.mongodb.com/download-center>`_.
 ---
 stepnum: 2
 level: 4