In the "all apps" screen, hit the 3-dots menu button upper right corner, then "show system", then scroll down to "SIM Toolkit" -- there, you've found it.
You didn't actually install it, and it didn't magically install. Its a system application that is delivered as part of the system image. The reason you are seeing an "update" for it in aurora is because there is a match in the package name.
If you try to "update" it from aurora store, the update will fail because the signature does not match between the open source version you have installed as part of the system image, and the google version on store.
Its nothing to worry about, just ignore it.
The package handles some configurations related to the sim card which can be found through the DIALER; 3-dots menu button --> Settings --> Calls --> Call forwarding, Additional settings.