Fix S2583/S2589 FN: Relational patterns are not supported

[Tim-Pohlmann]

void RelationalPattern(int i)
{
    if (i is > 6)
    {
        if (i is > 5)               // FN
            Console.WriteLine();
        if (i > 5)                  // FN
            Console.WriteLine();
    }
    if (i > 6)
    {
        if (i is > 5)               // FN
            Console.WriteLine();
        if (i > 5)                  // Noncompliant
            Console.WriteLine();
    }
}

Reproducers can be found here: https://github.com/SonarSource/sonar-dotnet/blob/69a33d3d99319522e98813aade3e4d920aaccbbd/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/SymbolicExecution/Roslyn/ConditionEvaluatesToConstant.CSharp9.cs#L31-L47