docs: add explanatory comment for robust datetime parsing fallback

- Add comment explaining that ab_datetime_try_parse handles ISO8601/RFC3339 formats
- Addresses PR feedback from @aaronsteers requesting documentation

Co-Authored-By: AJ Steers <aj@airbyte.io>

Author: devin-ai-integration[bot]

airbyte_cdk/sources/declarative/incremental/datetime_based_cursor.py

@@ -317,7 +317,7 @@ def parse_date(self, date: str) -> datetime.datetime:
 
         # If we have not parsed by now, use the robust parser which handles
         # all common formats, including all formats supported by ISO8601
-        # and RFC3306.
+        # and RFC3339.
         parsed_dt = ab_datetime_try_parse(date)
         if parsed_dt is not None:
             return parsed_dt