Fix degrees to radians

[Bigfoot71]

Corrects a small mistake in the comments and in the parameter name, which indicated degrees instead of radian.

Vector2Rotate() takes radians (source):

// Rotate vector by angle
RMAPI Vector2 Vector2Rotate(Vector2 v, float angle)
{
    Vector2 result = { 0 };

    float cosres = cosf(angle);
    float sinres = sinf(angle);

    result.x = v.x*cosres - v.y*sinres;
    result.y = v.x*sinres + v.y*cosres;

    return result;
}