Parentheses around multi-line `let` or `let!` block name

There is no information which style is preferred.


1)

```ruby
let :user do
  build(:user, profile: profile).tap do |user|
    user.save validate: false
  end
end
```

or

2) 

```ruby
let(:user) do
  build(:user, profile: profile).tap do |user|
    user.save validate: false
  end
end
```
