fix(tests/lean/norm_tac): display implicit parameters to make sure output can be parsed

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

tests/lean/norm_tac.lean

@@ -1,3 +1,4 @@
+SetOption pp::implicit true
 Variable vector (A : Type) (sz : Nat) : Type
 Variable read {A : Type} {sz : Nat} (v : vector A sz) (i : Nat) (H : i < sz) : A
 Variable V1 : vector Int 10

tests/lean/norm_tac.lean.expected.out

@@ -1,5 +1,6 @@
   Set: pp::colors
   Set: pp::unicode
+  Set: lean::pp::implicit
   Assumed: vector
   Assumed: read
   Assumed: V1