Simplify `cond ((locate-library "bbdb") ...)` by using `(when (require 'bbdb nil 'noerror) ...)`

https://github.com/jjuliano/practical.org.el/blob/da0da2ad23da2ed91b9a44f94d251467d414c074/practical.org.el#L303-L304

You could consider rewriting this as
```elisp
    (when (require 'bbdb nil 'noerror)
```
If `bbdb` can't be loaded, this returns `nil`, but if it can (or if `bbdb` is alreayd loaded), this return `bbdb` and the rest of the code will be executed.