Mutate `str.tr_s(pattern, '')` → `str.delete(pattern)`

These are equivalent:

```ruby
'222-333-4444'.tr_s('^0-9', '') # => "2223334444"
'222-333-4444'.delete('^0-9')   # => "2223334444"
```

Could probably also do that for `String#tr`. Honestly, I don't know the difference between `tr` and `tr_s` even after rereading the Ruby docs