[libcxx] [test] Remove two unnecesary files/variables in a test

[mstorsjo]

Summary

These don't seem to have any function in the test.

The non_regular_file one seems to have been added in 0f8c8f59df057a85d6d49913ec9877c6d597785b, without any apparent purpose there.

libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.copy_file/copy_file.pass.cpp

TEST_CASE(test_signatures) {
   ASSERT_NOT_NOEXCEPT(fs::copy_file(p, p, opts, ec));
 }
 
 TEST_CASE(test_error_reporting) {
 
   scoped_test_env env;
   const path file = env.create_file("file1", 42);
   const path file2 = env.create_file("file2", 55);
-  const path non_regular_file = env.create_fifo("non_reg");
-  const path dne = env.make_env_path("dne");
 
   { // exists(to) && equivalent(to, from)
     std::error_code ec;
     TEST_CHECK(fs::copy_file(file, file, copy_options::overwrite_existing,
                              ec) == false);
     TEST_CHECK(ErrorIs(ec, std::errc::file_exists));
     ExceptionChecker Checker(file, file, std::errc::file_exists, "copy_file");
     TEST_CHECK_THROW_RESULT(filesystem_error, Checker, copy_file(file, file, copy_options::overwrite_existing));