fix typo, clean up test_traceback_frame_removal (#3272)

Author: jakkdl

src/trio/_core/_tests/test_run.py

@@ -2130,17 +2130,12 @@ def check_traceback(exc: KeyError) -> bool:
         assert tb is not None
         return tb.tb_frame.f_code is my_child_task.__code__
 
-    expected_exception = Matcher(KeyError, check=check_traceback)
-
-    with RaisesGroup(expected_exception, expected_exception):
-        # Trick: For now cancel/nursery scopes still leave a bunch of tb gunk
-        # behind. But if there's an ExceptionGroup, they leave it on the group,
-        # which lets us get a clean look at the KeyError itself. Someday I
-        # guess this will always be an ExceptionGroup (#611), but for now we can
-        # force it by raising two exceptions.
+    with RaisesGroup(Matcher(KeyError, check=check_traceback)):
+        # For now cancel/nursery scopes still leave a bunch of tb gunk behind.
+        # But if there's an Exceptiongroup, they leave it on the group,
+        # which lets us get a clean look at the KeyError itself.
         async with _core.open_nursery() as nursery:
             nursery.start_soon(my_child_task)
-            nursery.start_soon(my_child_task)
 
 
 def test_contextvar_support() -> None:

tox.ini

@@ -68,7 +68,7 @@ deps =
     setuptools
     cython
 set_env =
-    CFLAGS= -DCYTHON_TRACE_NOGIL=1A
+    CFLAGS= -DCYTHON_TRACE_NOGIL=1
 allowlist_externals =
     sed
     cp