fix: remove duplicate error message
It seems like nvchecker emits two log entries for errors:
$ nvchecker --logger json -c .nvchecker.toml
{"logger_name": "nvchecker.core", "name": "curl", "event": "token not given but it is required", "level": "error"}
{"logger_name": "nvchecker.core", "name": "curl", "error": "token not given but it is required", "event": "no-result", "level": "error"}
This leads to a double error message as described in the related issue, which we fix by narrowing the selector to filter for the error entry.
Fixes #235 (closed)
Component: pkgctl version check