Tests: Fix FindMatlab.no_implicit_link_checks

matlab_add_mex uses the plain signature of target_link_libraries, so we need to use the plain signature also outside of matlab_add_mex to avoid a configuration error.

Note that in general users should use the LINK_TO option of matlab_add_mex, but this can't be used in this test as the point of the test is to check if the mex does not link some libraries, so we can't pass required libraries to LINK_TO.

Topic-rename: FindMatlab-test-no_implicit_link_checks