covr fails when curly brackets in ... arguments to dbplyr::build_sql()

Minimal reprex:

Define this function in a package:

```r
foo <- function() {
  src <- dbplyr::src_memdb()
  dbplyr::build_sql(
    {sql("foo")},
    con = src$con
  )
}
```

Then call it in a test. `testthat::test_check()` succeeds but `covr::package_coverage()` fails. Remove the curly brackets around `sql("foo")` and it succeeds.