Remove repeated import VectorInterface

Author: Yue-Zhengyuan

src/environments/bp_environments.jl

@@ -1,5 +1,5 @@
 struct BPEnv{T}
-    "4 x rows x cols array of message tensors, where the first dimension specifies the spactial direction"
+    "4 x rows x cols array of message tensors, where the first dimension specifies the spatial direction"
     messages::Array{T,3}
 end
 
@@ -71,8 +71,6 @@ end
 # VectorInterface
 # ---------------
 
-import VectorInterface as VI
-
 VI.scalartype(::Type{BPEnv{T}}) where {T} = scalartype(T)
 
 VI.zerovector(env::BPEnv, ::Type{S}) where {S<:Number} = BPEnv(zerovector.(env.messages, S))