DOCSP-13618 clarify that shutdown only applies to Linux; kill applies to Linux and macOS

Author: jmd-mongo

source/tutorial/manage-mongodb-processes.txt

@@ -150,8 +150,9 @@ authentication enabled.
 Use ``--shutdown``
 ~~~~~~~~~~~~~~~~~~
 
-From the Linux command line, shut down the :binary:`~bin.mongod` using the
-:option:`--shutdown <mongod --shutdown>` option in the following command:
+Supported on Linux only. From the command line, shut down the 
+:binary:`~bin.mongod` using the :option:`--shutdown <mongod --shutdown>`
+option:
 
 .. code-block:: sh
 
@@ -167,8 +168,9 @@ to perform a clean shutdown.
 Use ``kill``
 ~~~~~~~~~~~~
 
-From the Linux command line, shut down a specific :binary:`~bin.mongod` instance
-using one of the following commands:
+Supported on Linux and macOS only. From the command line, shut down a 
+specific :binary:`~bin.mongod` instance using one of the following 
+commands:
 
 .. code-block:: none