org-mac-link.el: Reduce Outlook App confusion

org-mac-link.el: Reduce Outlook App confusion

* org-mac-link.el (org-mac-outlook-message-open, org-as-get-selected-outlook-mail): Specify Microsoft Outlook.app non-ambiguously

If the user has:
- a virtual solution (Parallels, etc.)
- with Office for PC installed
- and configured to expose WinTel applications to the Macintosh Finder

The AppleScript commands may try to select the WinTel version of
"Microsoft Outlook". This—obviously—doesn’t work. By adding the Mac
~.app~ file extension and path, we reduce this confusion and more
reliably call the Macintosh version of Outlook.

TINYCHANGE

Signed-off-by: Alan Schmitt <alan.schmitt@polytechnique.org>