This PR promotes the allowance of the
[`clippy::single_range_in_vec_init`](https://rust-lang.github.io/rust-clippy/master/index.html#/single_range_in_vec_init)
rule to a permanent one.

This rule complains about a pretty common pattern we use that doesn't
seem to have any adverse effects, so we're going to continue allowing
this rule.

Release Notes:

- N/A