SQ -> Tests: Shell: _read_until: Rewrite to no longer use sleep() and…

… polling, preferring select() instead

src/crystal/tests/test_shell.py

@@ -803,7 +803,7 @@ def _read_until(
             if did_time_out:
                 # Look for an acceptable "stop suffix"
                 # Special case: '' is always an acceptable `stop_suffix`
-                if '' in stop_suffix_bytes_choices:
+                if '' in stop_suffix:
                     found_stop_suffix = ''
             else:
                 # Read stream