Un-deprecate Base.copy(::Langevin).

A generic copy function is needed for parallel tempering.

src/Integrators.jl

@@ -74,6 +74,9 @@ function Langevin(; λ=nothing, damping=nothing, kT)
     Langevin(NaN; λ, damping, kT)
 end
 
+function Base.copy(dyn::Langevin)
+    Langevin(dyn.dt; dyn.damping, dyn.kT)
+end
 
 #=
 Damping and noise terms may be included through the optional `damping` and `kT`

src/deprecated.jl

@@ -18,11 +18,6 @@ end
 Base.@deprecate suggest_magnetic_supercell(qs, latsize) suggest_magnetic_supercell(qs)
 Base.@deprecate offline_viewers() ()
 
-function Base.copy(dyn::Langevin)
-    @warn "Base.copy(dyn::Langevin) will break in Sunny v0.6! Use `Langevin(dyn.dt; dyn.damping, dyn.kT)` instead."
-    Langevin(dyn.dt; dyn.damping, dyn.kT)
-end
-
 function Base.getproperty(value::Langevin, name::Symbol)
     if name == :Δt
         @warn "`Δt` field is deprecated! Use `dt` instead."
@@ -61,4 +56,4 @@ end
 # λ argument in Langevin constructor
 # Δt argument in dynamical_correlations
 # large_S and biquad arguments in set_exchange! and set_exchange_at!
-# Argument `q` in set_spiral_order*
+# Argument `q` in set_spiral_order*