FIX HasManyList namespace

[ntd]

Description

When viewing a post with comments, I get the following error:

error-log.ERROR: Uncaught Exception TypeError: "SilverStripe\Comments\Model\Comment::AllReplies(): Return value must be of type ?SilverStripe\Model\List\HasManyList, SilverStripe\ORM\HasManyList returned" at ...

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