Fixed a code block in NEWS [ci skip]

A code block needs to be separated from the previous paragraph by
an empty line.

NEWS.md

@@ -384,6 +384,7 @@ Outstanding ones only.
 Excluding feature bug fixes.
 
 * Regexp literals and all Range objects are frozen [[Feature #8948]] [[Feature #16377]] [[Feature #15504]]
+
     ```ruby
     /foo/.frozen? #=> true
     (42...).frozen? # => true