nixos/pay-respects: fix "(eval):1: parse error near `alias'"
The README of pay-respects recommends the following for Bash and Zsh:
```sh
eval "$(pay-respects bash --alias)"
eval "$(pay-respects zsh --alias)"
```
The code in the NixOS module is missing the quotes.
This causes "(eval):1: parse error near `alias'" for me (using Zsh) and the alias `f` does not work.