Please revert this changeset - the feature you edited denotes the area of Folkestone predominantly containing residential buildings and has done so since it's creation 17 years ago, the artefact you are seeing is likely caused by a problem with the renderer or with a newly added feature. Please see https://wiki.openstreetmap.org/wiki/Tag:landuse%3Dresidential and https://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer 