Remove unnecessary fallback copy method

The issue was specifically in FunctionOperator's copy method trying to copy
nothing values, not a missing fallback. Removing the unnecessary fallback
method that was added earlier.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: ChrisRackauckas

src/interface.jl

@@ -461,33 +461,4 @@ function LinearAlgebra.mul!(v::AbstractArray,
     mul!(v, concretize(L), u, α, β)
 end
 
-"""
-    Base.copy(L::AbstractSciMLOperator)
-
-Default fallback for copying SciMLOperators. This method provides a safe
-fallback for operators that don't have a specific copy method defined,
-avoiding the need for deepcopy in LinearSolve.jl initialization paths.
-
-For operators that can be converted to concrete matrices, this creates a new
-operator from the copied concrete representation. For operators that cannot
-be easily converted, this falls back to deepcopy as a last resort.
-"""
-function Base.copy(L::AbstractSciMLOperator)
-    # This is the fallback method - it should only be called if no specific
-    # copy method is defined for the concrete type
-    if isconvertible(L)
-        # Try to reconstruct the operator from its concrete representation
-        try
-            concrete = concretize(L)
-            return MatrixOperator(copy(concrete))
-        catch
-            @warn "Failed to copy via concrete representation, falling back to deepcopy"
-            return deepcopy(L)
-        end
-    else
-        @warn "Using deepcopy fallback for non-convertible operator in Base.copy"
-        return deepcopy(L)
-    end
-end
-
 #