Fix for https://github.com/fluencelabs/aqua/blob/main/parser/src/main…

[potan]

Supporting blocks with "{}" in "given" definitions.

object {
  given g: Show[T] with {
    def show(x: T) = ""
  }
}

[susliko]

@potan Could you please provide a description for an issue addressed by this PR and a minimal piece of code which fails to be parsed by tree-sitter-scala parser?