Simplify AboveBelow a bit to avoid nested modules

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

Analysis/Sign.agda

@@ -42,22 +42,18 @@ open import Lattice.AboveBelow Sign _≡_ (record { ≈-refl = refl; ≈-sym = s
         ; ⊥ to ⊥ᵍ
         ; ⊤ to ⊤ᵍ
         ; [_] to [_]ᵍ
+        ; _≈_ to _≈ᵍ_
         ; ≈-⊥-⊥ to ≈ᵍ-⊥ᵍ-⊥ᵍ
         ; ≈-⊤-⊤ to ≈ᵍ-⊤ᵍ-⊤ᵍ
         ; ≈-lift to ≈ᵍ-lift
+        ; ≈-refl to ≈ᵍ-refl
         )
 -- 'sign' has no underlying lattice structure, so use the 'plain' above-below lattice.
-open AB.Plain using () renaming (finiteHeightLattice to finiteHeightLatticeᵍ-if-inhabited)
-
-finiteHeightLatticeᵍ = finiteHeightLatticeᵍ-if-inhabited 0ˢ
-
-open FiniteHeightLattice finiteHeightLatticeᵍ
-    using ()
+open AB.Plain 0ˢ using ()
     renaming
-        ( _≼_ to _≼ᵍ_
-        ; _≈_ to _≈ᵍ_
+        ( finiteHeightLattice to finiteHeightLatticeᵍ
+        ; _≼_ to _≼ᵍ_
         ; _⊔_ to _⊔ᵍ_
-        ; ≈-refl to ≈ᵍ-refl
         )
 
 plus : SignLattice → SignLattice → SignLattice