fix: update private-protected-properties-methods article.md en

[front42]

Private and protected properties and methods

Let's remove outdated information —
private properties and methods are part of the ECMAScript standard✅

[joaquinelio]

#3908
#3909

[front42]

Good PR, but they'll like this one better: sure we shouldn't mercilessly kill their favorite banner,
but quietly replace it with a more relevant one while they're sleeping😉

[joaquinelio]

Still,
none → new feels louder than a silent killing 🥷

[joaquinelio]

anyway, ¿does anyone know what [recent browser=none] is? "new" sounds like metadata [new addition] that adds preformated text.

[front42]

For some reason, the en-version hasn't contribution tips with "pre-made" banners mention, but the ru-version has,
perhaps they're stored somewhere. [recent browser="new"] appears here five times, [recent browser=Chrome] once,
[recent browser=none] once too, so maybe shortcodе-marker links similar preformatted text, none hints not supported.