Modify AWS supported services index

[fdalmaup]

Description

During the development of the Amazon Security Hub documentation (#6900), it was suggested to modify the :ref: command for the :doc: command (PR comment). The main reason for this change is that :doc: references the entire document without adding a custom anchor required by the :ref: use which generates a loading delay that needs to be manually modified.

This issue aims to replace every :ref: command used in source/cloud-security/amazon/services/supported-services/index.rst with :doc:, removing the custom anchor from each document to be consistent with the required change and avoid manually crafted modifications when a native one can be used.