chore(widgets): remove unneeded nullish coalescing

[ShGKme]

☑️ Resolves

!!expression returns boolean and cannot return undefined/null anyway. And if it is falsy, then it is false already.

[plugin:vite:esbuild] [plugin vite:esbuild] src/functions/reference/widgets.ts: The "??" operator here will always return the left operand
42 |  
43 |  export const hasFullWidth = (id: string) => {
44 |    return !!window._vue_richtext_widgets[id]?.fullWidth ?? false
   |                                                        ^
45 |  }
46 | 

[ShGKme]

/backport to next