tests: Remove skipped tests hack for Cmake < 3.9.0

We require 3.19

This also makes skipped tests visible, which showed that the
print-help test was never run because the REQUIRES line was off.

In sh-mode, bash's `command -v` returns true if *all* commands exist.

tests/checks/print-help.fish

@@ -1,6 +1,6 @@
 # RUN: %fish %s
 # Test redirecting builtin help with a pipe
-# REQUIRES: command -v mandoc nroff
+# REQUIRES: command -v mandoc || command -v nroff
 
 set -lx __fish_data_dir (mktemp -d)
 mkdir -p $__fish_data_dir/man/man1

tests/test_driver.sh

@@ -68,14 +68,5 @@ fish_init_cmd="${fish_init_cmd} && source ${TESTS_ROOT}/test_util.fish";
     --init-command "${fish_init_cmd}" "$fish_script" "$script_args")
 test_status="$?"
 
-# CMake less than 3.9.0 "fully supports" setting an exit code to denote a skipped test, but then
-# it just goes ahead and reports them as failed anyway. Really?
-if test -n $CMAKE_SKIPPED_HACK; then
-    if test $test_status -eq 125; then
-        echo "Overriding SKIPPED return code from test" 1>&2
-        test_status=0
-    fi
-fi
-
 rm -rf "$homedir"
 exit "$test_status"