bug#67669: 29.1; Drop text suggesting using `and' to replace `if'

[Drew Adams]

> (let (baz)
>   (setq foo (concat "bar" (if (stringp baz) baz))))
>   => "bar"
> 
> Here 'if' returns nil, and we use the feature of
> 'concat' to ignore nil arguments.

IMO the meaning/behavior is clearer with `and':

 (let (baz)
   (setq foo (concat "bar" (and (stringp baz) baz))))

But again, such stylistic concerns are exactly that.