Clean up TODO comments for new room list

All relevant TODOs should still be present, and reference an issue for easy finding.

src/components/structures/RoomSearch.tsx

@@ -25,6 +25,8 @@ import { Key } from "../../Keyboard";
 import AccessibleButton from "../views/elements/AccessibleButton";
 import { Action } from "../../dispatcher/actions";
 
+// TODO: Remove banner on launch: https://github.com/vector-im/riot-web/issues/14231
+
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