Add NEWS.md entry for bitbroadcast deprecation (#19771). (#21804)

Author: Sacha0

NEWS.md

@@ -440,6 +440,9 @@ Deprecated or removed
   * The zero-argument constructor `MersenneTwister()` has been
     deprecated in favor of the explicit `MersenneTwister(0)` ([#16984]).
 
+  * `bitbroadcast` has been deprecated in favor of `broadcast`, which now produces a
+    `BitArray` instead of `Array{Bool}` for functions yielding a boolean result ([#19771]).
+
 <!--- generated by NEWS-update.jl: -->
 [#265]: https://github.com/JuliaLang/julia/issues/265
 [#4615]: https://github.com/JuliaLang/julia/issues/4615
@@ -512,6 +515,7 @@ Deprecated or removed
 [#19722]: https://github.com/JuliaLang/julia/issues/19722
 [#19724]: https://github.com/JuliaLang/julia/issues/19724
 [#19741]: https://github.com/JuliaLang/julia/issues/19741
+[#19771]: https://github.com/JuliaLang/julia/issues/19771
 [#19784]: https://github.com/JuliaLang/julia/issues/19784
 [#19787]: https://github.com/JuliaLang/julia/issues/19787
 [#19791]: https://github.com/JuliaLang/julia/issues/19791