fix: do not distribute_shift inside Sample and Hold

Author: AayushSabharwal

src/structural_transformation/utils.jl

@@ -593,7 +593,7 @@ end
 function _distribute_shift(expr, shift)
     if iscall(expr)
         op = operation(expr)
-        (op isa Pre || op isa Initial) && return expr
+        (op isa Union{Pre, Initial, Sample, Hold}) && return expr
         args = arguments(expr)
 
         if ModelingToolkit.isvariable(expr) && operation(expr) !== getindex