test.py: Run relay pair/vanish on macOS CI again

It passed on the macOS runner three times out of three after the fix for
relay sends and receives off the network.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test.py

@@ -634,11 +634,6 @@ if platform.system() == "Windows":
   # Windows retries a refused TCP connect for about a second before reporting it, which at the tests'
   # 800% speed is far longer than a PSP's refusal.
   pair_known_failures["p2p"].append("net/adhoc/pair/basic")
-if platform.system() == "Darwin" and os.environ.get("CI"):
-  # On macOS CI runners only, and with the instances in step: once the client has gone, the host's
-  # matching drops it without the TIMEOUT event (no events at all), and SendData says NOT_ESTABLISHED.
-  # Not reproduced on a Mac or on the other runners yet.
-  pair_known_failures["relay"].append("net/adhoc/pair/vanish")
 
 ADHOC_MODES = ["relay", "p2p"]