Fix bug with printing pinned dependencies.
Fix bug with printing pinned dependencies.

Brew prints this error:
```
Error: undefined method `join' for nil:NilClass
```

because, in this code:

```ruby
puts pinned_dependents.map do |f|
  "#{f.full_specified_name} #{f.pkg_version}"
end.join(", ")
```
the block is passed to `puts` and not to `map`. `.join(",")` is called on the output of `puts`.

(I think the regression was introduced in this commit: e12a7b0808353ea81d63774be1edaff81710d7a6)

konqui/brew,mahori/brew,JCount/brew,Homebrew/brew,vitorgalvao/brew,Homebrew/brew,konqui/brew,nandub/brew,EricFromCanada/brew,claui/brew,vitorgalvao/brew,mahori/brew,MikeMcQuaid/brew,EricFromCanada/brew,claui/brew,nandub/brew,EricFromCanada/brew,konqui/brew,nandub/brew,claui/brew,reitermarkus/brew,reitermarkus/brew,JCount/brew,reitermarkus/brew,Homebrew/brew,EricFromCanada/brew,vitorgalvao/brew,sjackman/homebrew,nandub/brew,mahori/brew,MikeMcQuaid/brew,Homebrew/brew,sjackman/homebrew,claui/brew,reitermarkus/brew,sjackman/homebrew,vitorgalvao/brew,konqui/brew,sjackman/homebrew,MikeMcQuaid/brew,JCount/brew,mahori/brew,MikeMcQuaid/brew,JCount/brew