Trim option's innerHTML to allow searching in weird HTML code

With this change, if the HTML is (note the linebreaks)

```
<option>
    string
</option>
```

chosen will now find this option when searching for "st".
replace trim() by compatible code

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim?redirectlocale=en-US&redirectslug=JavaScript%2FReference%2FGlobal_Objects%2FString%2FTrim#Compatibility
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