refactor: remove dnscheck loader (#1640)

## Checklist

- [x] I have read the [contribution
guidelines](https://github.com/ooni/probe-cli/blob/master/CONTRIBUTING.md)
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- [ ] if you changed anything related to how experiments work and you
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## Description

This diff refactors the dnscheck factory to use the default target
loader

docs/design/dd-008-richer-input.md

@@ -4,7 +4,7 @@
 |--------------|------------------------------------------------|
 | Author       | [@bassosimone](https://github.com/bassosimone) |
 | Last-Updated | 2024-07-02                                     |
-| Reviewed-by  | [@DecFox](https://github.com/DecFox            |
+| Reviewed-by  | [@DecFox](https://github.com/DecFox)           |
 | Status       | living document                                |
 
 This document is a living document documenting our in-progress design

internal/registry/dnscheck.go

@@ -22,7 +22,6 @@ func init() {
 			config:           &dnscheck.Config{},
 			enabledByDefault: true,
 			inputPolicy:      model.InputOrStaticDefault,
-			newLoader:        dnscheck.NewLoader,
 		}
 	}
 }