docs: duplicate 'the' in OCI image index scan summary

## Description

In `docs/administration/vulnerability-scanning/scan-individual-artifact.md`, the successful OCI image index scan note says:

> aggregated from the individual scan results of the the artifacts referenced by the index

Please remove the duplicate "the" so it reads "of the artifacts".

## Why

Minor docs grammar fix for clarity.

Open docs/administration/vulnerability-scanning/scan-individual-artifact.md and find the successful OCI image index scan note. Remove the duplicated "the" so the sentence reads "of the artifacts", then review the rendered wording or diff to confirm the grammar fix.

Written by the indexing model from the issue text.