incorrect Float64 assumptions in diff_to_zero

[isaacsas]

Catalyst.jl/src/reactionsystem.jl

Line 1632 in 2276e1c

diff_2_zero(expr) = (Symbolics.is_derivative(expr) ? 0.0 : expr)

seems problematic. We shouldn't be assuming a type. This whole code path should probably just delete the derivative terms instead of setting them to zero to avoid making assumptions about types.