Policy breaks deprecation

[elacaille18]

Context

This PR handles the deprecation of policy breaks

What has been done

• correct the Readme

Validation

PR check list

• [ ] If the changes affect the end user (new feature, behavior change, bug fix) then the PR has a changelog entry (see doc/dev/getting-started.md). If the changes do not affect the end user, then the skip-changelog label has been added to the PR.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.97%. Comparing base (6f90c8e) to head (ade73ea).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1004 +/- ## ======================================= Coverage 91.97% 91.97% ======================================= Files 181 181 Lines 7655 7655 ======================================= Hits 7041 7041 Misses 614 614 ``` | [Flag](https://app.codecov.io/gh/GitGuardian/ggshield/pull/1004/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GitGuardian) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/GitGuardian/ggshield/pull/1004/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GitGuardian) | `91.97% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GitGuardian#carryforward-flags-in-the-pull-request-comment) to find out more.

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