One way to directly have what you want is using the mutable keyword - https://observablehq.com/@observablehq/introduction-to-mutable-state. But it’s not very recommended, and another way could be to create an .update() method in your svg chart, and call it when the input option changes a value, without direct dependency between the input cell and the svg cell.
See A bit confused about 'mutable', etc for more about the different ways of synchronizing the states of two “views”
See also another thread about the same problem: how to control cell updating in response to value changes in dependency cells?