tests: line: remove a bad test case

tests: line: remove a bad test case

The test case for requesting multiple lines exposed by different chips
has never been correct. The request call does indeed fail with EINVAL
but now that we've disallowed adding lines from different chips to
the same bulk object, this happens only because we're using a wrong
constant in the flags field of the request structure.

Remove the entire test as it's no longer required.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>