pytester: spawn: do not skip FreeBSD

Fixes https://github.com/pytest-dev/pytest/issues/6069

changelog/6069.improvement.rst

@@ -0,0 +1 @@
+``pytester.spawn`` does not skip/xfail tests on FreeBSD anymore unconditionally.

src/_pytest/pytester.py

@@ -1194,8 +1194,6 @@ class Testdir:
         pexpect = pytest.importorskip("pexpect", "3.0")
         if hasattr(sys, "pypy_version_info") and "64" in platform.machine():
             pytest.skip("pypy-64 bit not supported")
-        if sys.platform.startswith("freebsd"):
-            pytest.xfail("pexpect does not work reliably on freebsd")
         if not hasattr(pexpect, "spawn"):
             pytest.skip("pexpect.spawn not available")
         logfile = self.tmpdir.join("spawn.out").open("wb")