MobileSafari falsely claims CSS resize property support

[Bramus]

Recently I wrote an article on using CSS `resize: both;`: https://www.bram.us/2020/05/15/css-only-resizable-elements/

In browsers that don't support this property I wanted to show a warning on screen to notify users thereof. For this I use an @supports rule:

```css
.warning {
    display: block;
}

/* Hide warning in case browser supports resize: both; */
@supports (resize: both) {
    .warning {
        display: none;
    }
}
```

I've come to notice that MobileSafari – which does not support `resize: both;` – hides the warning and thus falsely claims to support said CSS resize property.

Demo: https://codepen.io/bramus/pen/RwWeqOP

[Radar WebKit Bug Importer]

<rdar://problem/63335059>