Update NEWS.md

Author: fverdugo

NEWS.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [0.16.0] - Unreleased
+## [0.16.0] - 2021-06-04
 
 ### Added
 - User API to select specific quadrature rules. Since PR [#578](https://github.com/gridap/Gridap.jl/pull/578).