R4: drop stale line-number ref in path_sup_t_bands comment

CI AI review R3 P3: the comment referenced
chaisemartin_dhaultfoeuille.py:2865-2875 but the OVERALL
event_study_effects[l]['cband_conf_int'] propagation now lives at
~3329-3338 in the same file. The OVERALL site is inlined inside
fit() with no stable enclosing function name, so the cleanest fix
is to drop the line range entirely and reference the symbol +
enclosing fit() method (stable across moves). Per feedback memory
'audit-residual-drift-classes' item 6 (Hardcoded line refs).

Author: igerber

diff_diff/chaisemartin_dhaultfoeuille_results.py

@@ -629,8 +629,9 @@ class ChaisemartinDHaultfoeuilleResults:
     # a positive int OR `paths_of_interest` is non-empty AND
     # `n_bootstrap > 0`. The joint band itself is written per-horizon as
     # `cband_conf_int` on `path_effects[path]["horizons"][l]` (mirrors
-    # the OVERALL `event_study_effects[l]["cband_conf_int"]` pattern at
-    # `chaisemartin_dhaultfoeuille.py:2865-2875`). Empty-state contract:
+    # the OVERALL `event_study_effects[l]["cband_conf_int"]` pattern
+    # populated alongside the bootstrap propagation in
+    # `chaisemartin_dhaultfoeuille.py::fit`). Empty-state contract:
     # `None` when not requested (no bootstrap, or both `by_path` and
     # `paths_of_interest` are `None`); `{}` when requested but no path
     # passed both gates (>=2 valid horizons AND a strict majority — more