Fix an unknown trust error when updating a package in Arch Linux

The steps below outline how to fix an unknown trust error when upgrading a package in Arch Linux.

While trying to update the package polkit, I encountered the following error:

error: polkit: signature from <USER> <EMAIL> is unknown trust
:: File /var/cache/pacman/pkg/polkit-0.119-1-x86_64.pkg.tar.zst is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] n
error: failed to commit transaction (invalid or corrupted package (PGP signature))
Errors occurred, no packages were upgraded.

The issue was that my keys were out of date. I ran the following command to refresh my keys:

$ sudo pacman-key --refresh-keys

After that, I was able to use pacman to update the package without issues.