Remove NEWS entry about taint deprecation warnings [ci skip]

JunichiIto on GitHub correctly pointed out this is no longer
accurate due to the change to not display deprecation warnings by
default.

Author: jeremyevans

NEWS.md

@@ -503,9 +503,6 @@ end
   splats, those are now removed just as they are for methods not
   using `ruby2_keywords`.
 
-* Taint deprecation warnings are now issued in regular mode in
-  addition to verbose warning mode.  [[Feature #16131]]
-
 * When an exception is caught in the default handler, the error
   message and backtrace are printed in order from the innermost.
   [[Feature #8661]]