Ripgrep zsh autocompletion no longer installs after 14.x upgrade

[John Howard]

After upgrading to Ripgrep 14, zsh autocompletion is no longer installed properly

Ripgrep 14 includes /usr/share/zsh/vendor-completions/rg.zsh
Ripgrep 12 includes /usr/share/zsh/vendor-completions/_rg

The 14 one is invalid, I think the function requires the naming scheme (not certain).

Reproducer:

```
$ docker run -it ubuntu:noble
root@68026c046d27:/# apt update; apt install -y zsh ripgrep
root@68026c046d27:/# zsh
68026c046d27# autoload -Uz compinit; compinit
68026c046d27# for key val in "${(@kv)_comps}"; do
    echo "$key -> $val"
done | rg rg
# No completion defined
68026c046d27# mv /usr/share/zsh/vendor-completions/rg.zsh /usr/share/zsh/vendor-completions/_rg
68026c046d27# autoload -Uz compinit; compinit
68026c046d27# for key val in "${(@kv)_comps}"; do
    echo "$key -> $val"
done | rg rg
rg -> _rg
```

This also applies to debian's packaging

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.