`given` block doesn't work without braces

## minimized code

```Scala

given
  def (i: Int) pow2 = i * i

println(5.pow2)
```

## expectation

Code compiles

## reality

```
[error] 2 |  def (i: Int) pow2 = i * i
[error]   |^^^
[error]   |an identifier expected, but 'end of statement' found
[error] one error found
```