Fix S1118 FN: empty primary constructor

[cristian-ambrosini-sonarsource]

The rule does not take into account when the class is defining an empty primary constructor.

public class PrimaryCtor() // FN
{
    public static string Concatenate(string s1, string s2)
    {
        return s1 + s2;
    }

    public static string Prop { get; set; }
}