less subtlety when downgrading a package

I did `Pkg.add(Winston)` and was surprised when `Compat` stopped containing functionality I'd expected there. Looking back very closely, I noticed:
```
  [34da2185] ↓ Compat v3.13.0 ⇒ v2.2.0
```

But that's quite subtle! Can we print a warning message at the bottom in bold:

```
Downgraded 4 packages while installing to satisfy version bounds.
```