[interpreter] Add a missing closing parens

Missed it in #466.

Author: ngzhian

interpreter/exec/simd.ml

@@ -450,7 +450,7 @@ struct
     let trunc_sat_f32x4_u = convert I32_convert.trunc_sat_f32_u
 
     let convert_zero f v =
-      Rep.(of_i32x4 I32.(zero :: zero :: (List.map f (to_f64x2 v)))
+      Rep.(of_i32x4 I32.(zero :: zero :: (List.map f (to_f64x2 v))))
     let trunc_sat_f64x2_s_zero = convert_zero I32_convert.trunc_sat_f64_s
     let trunc_sat_f64x2_u_zero = convert_zero I32_convert.trunc_sat_f64_u