Description of proposed changes

As mentioned in #3244 (comment):

The pygmt.print_clib_info function was initially added in #176 but has been replaced by pygmt.show_versions in #466 (first appear in v0.1.2).

In this PR, a new private function _get_clib_info is added which returns a dictionary instead of printing a long string.

It's time to retire the print_clib_info function. Since it's rarely used, I think we can just remove it without a deprecation warning. Of course, we should do it in a separate PR so that at least we have a deprecation entry in the v0.13.0 changelog.

This PR removes the print_clib.info function.