docs(changelog): add the #1705 fragment

Co-Authored-By: Claude Fable 5.2 <[email protected]>

changelog.d/1705-traffic-road-load.md

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+- Cut the stutter while zooming and panning with Street Traffic on in dense
+  cities. Coarse roads are no longer clipped against every detail tile in one
+  task, roads already parsed in a load are not parsed again, and ground floors
+  are read once per cell (mazy1998, #1705).