Wrong width calculation for non-syntactic names

They are escaped twice, tibbles with many such columns may have columns removed without apparent reason.

``` r
print(tibble::tibble("mean(x)" = 5, "var(x)" = 3), width = 28)
#> # A tibble: 1 x 2
#>   `mean(x)`
#>       <dbl>
#> 1         5
#> # ... with 1 more
#> #   variables:
#> #   `var(x)` <dbl>
```