code_highlight() trims long strings

This is the cli counterpart of prettycode's https://github.com/r-lib/prettycode/issues/20

``` r
x <- paste0('"', strrep("-", 1000), '"')
cli::code_highlight(x)
#> [1] "[1000 chars quoted with '\"']"
```

<sup>Created on 2024-09-30 with [reprex v2.1.0](https://reprex.tidyverse.org)</sup>

Would you like a PR?