Update libmspub.rb

Removing extraneous test code as per suggestion from libreoffice dev @dtardon
new test pasts test successfully
That depends on what the test is actually supposed to test... If it is just to ensure that compiling/linking with the library works, then not. If it also checks that the library is installed in the right place, then it should be run and the line needs to be added back.

(I do not know, as I first heard of homebrew a few days ago...)