Update Manager uses the wrong destination for keyrings

[SineSwiper]

Describe the bug
The "Add missing keys" button adds keys to /etc/apt/trusted.gpg.d/. This is wrong, because the keyrings have been moved to /usr/share/keyrings. The apt command does not look in /etc/apt/trusted.gpg.d/, so this button doesn't do anything useful.

Furthermore, this may impact other tools within Update Manager that interact with keyrings.

Screenshots

To Reproduce

1. Software Sources > Maintenance > Add missing keys
2. ls -l /etc/apt/trusted.gpg.d/
3. See keys updated in bad location

Expected behavior
Keys in /usr/share/keyrings

Distribution:
Linux Mint

Software version:
7.1.4

Logs:
Nothing relevant.