If you are only referring to the InfoCenter, are you open to removing InfoCenter completely? I don't know of a way to kill the messages while leaving InfoCenter intact.
If so, put this in your "acad.lsp" file (create it if needed), and restart AutoCAD twice.
Code:
;; Disable InfoCenter
(vl-registry-write
(strcat "HKEY_CURRENT_USER\\" (vlax-product-key) "\\InfoCenter")
"InfoCenterOn"
0
)
If you're referring to all tooltips, such as those that appear on commands in the Ribbon, etc. that is a different precedure.