fix import issues

Author: schillic

src/MathematicalPredicates.jl

@@ -10,7 +10,7 @@ include("Conjunction.jl")
 include("Disjunction.jl")
 
 # optional dependencies
-using Requires
+using Requires: @require
 include("init.jl")
 
 end  # module

src/init_LazySets.jl

@@ -5,7 +5,8 @@ import .LazySets: dim, project
     import Base: contains
 end
 
-using .LazySets: LazySet, ⊆, isdisjoint
+using Base: ⊆, isdisjoint
+using .LazySets: LazySet
 
 """
     SetAtom{S<:LazySet, T} <: Predicate{Val{1}}