Add changelog entry for opentripplanner#6401 [ci skip]

Author: OTP Changelog Bot

doc/user/Changelog.md

@@ -109,6 +109,7 @@ based on merged pull requests. Search GitHub issues and pull requests for smalle
 - Support for coordinates in via search [#6477](https://github.com/opentripplanner/OpenTripPlanner/pull/6477)
 - Use default max stop count for mode from routing defaults in transfer requests [#6494](https://github.com/opentripplanner/OpenTripPlanner/pull/6494)
 - Temporarily restore debug layers to classic debug UI and change grouping of safety layers in the new one [#6497](https://github.com/opentripplanner/OpenTripPlanner/pull/6497)
+- Conditionally wait for previous polling task [#6401](https://github.com/opentripplanner/OpenTripPlanner/pull/6401)
 [](AUTOMATIC_CHANGELOG_PLACEHOLDER_DO_NOT_REMOVE)
 
 ## 2.6.0 (2024-09-18)