The dash should be “- -” (without space) instead. But those get somehow merged by the forum software during the post. It also works without them though.
The error is the same issue as here: the following signatures were invalid: EXPKEYSIG 74A941BA219EC810 deb.torproject.org archive signing key - #3 by Patrick
You can try to install the latest deb.torproject.org-keyring package and see if it gets fixed.
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