test(gateway): drop source-reading guard test from #71671 salvage

Source-regex tests are banned (AGENTS.md 'Never read source code in
tests') — keep only the behavioral regression test.

contributors/emails/hereicq@users.noreply.github.com

@@ -0,0 +1 @@
+hereicq

tests/gateway/test_71671_faulthandler_no_stderr.py

@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 import faulthandler
-import os
 import sys
 
 import pytest
@@ -33,15 +32,3 @@ def test_faulthandler_enable_falls_back_when_stderr_is_none(tmp_path):
         sys.stderr = real_stderr
         if was_enabled:
             faulthandler.enable()
-
-
-def test_gateway_run_keeps_faulthandler_guard():
-    src = os.path.join(
-        os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))),
-        "gateway", "run.py",
-    )
-    with open(src, encoding="utf-8") as f:
-        text = f.read()
-    assert "try:\n            faulthandler.enable()\n        except (RuntimeError, ValueError, OSError):" in text, (
-        "gateway/run.py must keep the try/except guard around faulthandler.enable() (see #71671)"
-    )