Move proper-list-p tests to fns-tests.el

This follows the move of proper-list-p from lisp/subr.el to
src/fns.c in 2018-07-24T15:58:46-07:00!eggert@cs.ucla.edu.
* test/lisp/subr-tests.el (subr-tests--proper-list-p): Move from
here...
* test/src/fns-tests.el (test-proper-list-p): ...to here.
parent 9a54e70c
Pipeline #1256 failed with stage
in 50 minutes and 11 seconds