Removed unused parameter

Author: agronholm

trio/_core/_run.py

@@ -475,7 +475,7 @@ def __enter__(self):
             task._activate_cancel_status(self._cancel_status)
         return self
 
-    def _close(self, exc, collapse=False):
+    def _close(self, exc):
         if self._cancel_status is None:
             new_exc = RuntimeError(
                 "Cancel scope stack corrupted: attempted to exit {!r} "