fix(test): remove flaky "other port not reachable" assertion

The assertion that a randomly allocated port should not be reachable
is prone to race conditions on CI with parallel test workers, as
another process may bind to that port during the polling window.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: stackia

tools/e2e/test_config.py

@@ -55,9 +55,6 @@ def test_listen_port(self, r2h_binary):
             r2h.start()
             # Port should be reachable
             assert wait_for_port(port)
-            # Different port should NOT be reachable
-            other_port = find_free_port()
-            assert not wait_for_port(other_port, timeout=0.3)
         finally:
             r2h.stop()