[Flang] Update Extensions.md for supported BIND(C) LOGICAL kind. (#88159)

Flang also supports non-scalar logical dummy argument with a different
KIND from C_BOOL to a bind(c) routine as well as a component in a
bind(c) derived type. Update the document.

```
subroutine sub(arg)
logical(4) :: arg(4)
end
```

```
type dt
logical(4) :: comp
end type
end
```