Drop the Attributes version

[DaveLiddament]

Reasons for dropping the proposed Attributes version of annotating code (see example below):

• Not supported and a perfectly acceptable alternative exists (docblocks)
• Would require static analysis tool authors to do extra work to support it.
• Is it actually better than docblocks?

use StaticAnalysis\Generics\v1\Template;
use StaticAnalysis\Generics\v1\Type;

#[Template("T")] 
#[Type("array<int,T>")]    // This is documenting the return type
function asArray(
    #[Type("T")] $value,
) { 
    return [$value]; 
}

..