[CssSelector] Fix :nth-last-child() translation

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8068
| License       | MIT
| Doc PR        | n/a

Same as #8072, but for < 2.3