Fix requires_update_callback of shifting techniques (#925)

Co-authored-by: Sven Berger <[email protected]>

Author: efaulhaber

src/schemes/fluid/shifting_techniques.jl

@@ -7,7 +7,7 @@ abstract type AbstractShiftingTechnique end
 # The version for a specific system type will override this generic version.
 requires_update_callback(system) = requires_update_callback(shifting_technique(system))
 requires_update_callback(::Nothing) = false
-requires_update_callback(::AbstractShiftingTechnique) = true
+requires_update_callback(::AbstractShiftingTechnique) = false
 
 # This is called from the `UpdateCallback`
 particle_shifting_from_callback!(u_ode, shifting, system, v_ode, semi, dt) = u_ode
@@ -302,6 +302,10 @@ function ConsistentShiftingSun2019(; kwargs...)
                                      kwargs...)
 end
 
+# `ParticleShiftingTechnique{<:Any, false}` means `update_everystage=false`,
+# so the `UpdateCallback` is required to update the shifting velocity.
+requires_update_callback(::ParticleShiftingTechnique{<:Any, false}) = true
+
 # `ParticleShiftingTechnique{false}` means `integrate_shifting_velocity=false`.
 # Zero if PST is applied in a callback as a position correction
 # and not with a shifting velocity in the time integration stages