Replace with `sort.Ints(x)`, `sort.Float64s(x)`, `sort.Strings(x)`

The `sort.Ints`, `sort.Float64s` and `sort.Strings` functions are
easier to read than `sort.Sort(sort.IntSlice(x))`,
`sort.Sort(sort.Float64Slice(x))` and
`sort.Sort(sort.StringSlice(x))`.

**Before:**

```
sort.Sort(sort.StringSlice(x))
```

**After:**

```
sort.Strings(x)
```
