JIT: Redundant bound check

```cs
static bool ParseIP(string s)
{
    if (s.Length > 15)
    {
        return false;
    }

    Span<ushort> value = stackalloc ushort[16];
    value[s.Length] = '.';
    Consume(value);
    return true;
}


[MethodImpl(MethodImplOptions.NoInlining)]
static void Consume<T>(Span<T> _)
{
}
```

Currently, `value[s.Length] = '.';` line produces a bound check while it shouldn't.