Add new allowed deprecation warnings for cufflinks

Added two deprecation warning messages related to DatetimeIndex.format and Series.__getitem__ to the app_allow_external_errors list, as these are triggered by the cufflinks package.

Author: karangattu

tests/playwright/examples/example_apps.py

@@ -94,6 +94,8 @@ def get_apps(path: str) -> typing.List[str]:
     "FutureWarning: use_inf_as_na option is deprecated",
     "pd.option_context('mode.use_inf_as_na",  # continutation of line above,
     "RuntimeWarning: invalid value encountered in dot",  # some groups didn't have enough data points to create a meaningful line
+    "DatetimeIndex.format is deprecated and will be removed in a future version. Convert using index.astype(str) or index.map(formatter) instead.",  # cufflinks package is using this method
+    "Series.__getitem__ treating keys as positions is deprecated. In a future version, integer keys will always be treated as labels (consistent with DataFrame behavior). To access a value by position, use `ser.iloc[pos]`",  # cufflinks package is using this method
 ]
 app_allow_js_errors: typing.Dict[str, typing.List[str]] = {
     "examples/brownian": ["Failed to acquire camera feed:"],