fix(rust/signed-doc): DocumentOwnershipRule where it can cause panic during validation

[apskhem]

Description

• Removed the code inside DocumentOwnershipRule where it can cause panic during validation, especially when the Provider is empty.

Related Issue(s)

Resolves #3831

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

📚 Docs Preview

The docs for this PR can be previewed at the following URL:

https://docs.dev.projectcatalyst.io/libs/fix/ownership-rule-validation

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 605/605}$ | ${\color{red}Fail: 0/605}$ |

[Mr-Leshiy]

LGTM