remove Tighten stuff

golden-tests/tests/useless-coe/coe.quox

@@ -0,0 +1,9 @@
+-- non-dependent coe should reduce to its body
+
+def five  : ℕ = 5
+def five? : ℕ = coe ℕ 5
+
+def eq : five ≡ five? : ℕ = δ _ ⇒ 5
+
+def subst1 : 0.(P : ℕ → ★) → P five  → P five? = λ P p ⇒ p
+def subst2 : 0.(P : ℕ → ★) → P five? → P five  = λ P p ⇒ p

golden-tests/tests/useless-coe/expected

@@ -0,0 +1,5 @@
+ω.five : ℕ
+ω.five? : ℕ
+ω.eq : five ≡ five? : ℕ
+ω.subst1 : 0.(P : 1.ℕ → ★) → 1.(P five) → P five?
+ω.subst2 : 0.(P : 1.ℕ → ★) → 1.(P five?) → P five

golden-tests/tests/useless-coe/run

@@ -0,0 +1,2 @@
+. ../lib.sh
+check "$1" coe.quox