Review technical content: Desktop Wallet shared accounts - credentials

Technical review of the credential management features under "Shared accounts with multiple credentials in Desktop Wallet" to verify technical accuracy and completeness.

Review focus:

* Correctness of all technical information
* Completeness of information
* Removal of irrelevant or redundant information

Review is complete when:

* All technical information has been verified
* Missing information has been identified and added
* Irrelevant or redundant information has been deleted
* PR with necessary changes has been submitted

Pages to review:

1. [Shared accounts with multiple credentials in Desktop Wallet:](https://docs.concordium.com/en/mainnet/docs/guides/overview-shared-accounts.html#) [https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/guides/overview-shared-accounts.rst](https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/guides/overview-shared-accounts.rst)
2. [Create a credentials file](https://docs.concordium.com/en/mainnet/docs/desktop-wallet/create-credentials-file.html): [https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/desktop-wallet/create-credentials-file.rst](https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/desktop-wallet/create-credentials-file.rst)
3. [Add credentials to an account](https://docs.concordium.com/en/mainnet/docs/guides/multi-credentials.html): [https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/guides/multi-credentials.rst](https://github.com/Concordium/concordium.github.io/blob/main/source/mainnet/docs/guides/multi-credentials.rst)

Note: A separate review of language and style will be conducted after the technical review is complete.