tests: remove an obsolete test script * t/scripts.sh: This: it used to check that the 'AC_PROG_INSTALL' macro was not uselessly required, but today that macro is AC_REQUIRE'd by 'AM_INIT_AUTOMAKE' anyway, so that the test is no more significant. * t/list-of-tests.mk: Adjust. Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>