[SDTEST-3123] Update Flaky Tests Management docs

[TovRudyy]

What does this PR do? What is the motivation?

Updating the docs of Flaky Tests Management documenting the new "Failure rate" automatic rule.

Updating mentions of "Flaky Test Management" to "Flaky Tests Management" for coherence. In our DataDog UI, the product is called "Flaky Tests Management".

Merge instructions

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Do not merge after approving.

• Ready for merge

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Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/olek.rudyy/update-ftm-docs/tests/flaky_management/

[estherk15]

Left a suggestion to fix the list formatting, but approved!

[estherk15]

Suggested change

| **Quarantine** | Toggle to allow flaky tests to be quarantined for this repository. Customize automation rules based on: <li>Time: Quarantine a test if its status is `Active` for a specified number of days. The rule is triggered every day at 12:15 UTC. <li>Branch: Quarantine an `Active` test if it flakes in one or more specified branches. <li>Failure rate: Quarantine an `Active` test if its failure rate over the last 7 days is greater or equal to the specified threshold. The rule is triggered every 15 minutes. |

| **Quarantine** | Toggle to allow flaky tests to be quarantined for this repository. Customize automation rules based on: <ul><li>Time: Quarantine a test if its status is `Active` for a specified number of days. The rule is triggered every day at 12:15 UTC. <li>Branch: Quarantine an `Active` test if it flakes in one or more specified branches. <li>Failure rate: Quarantine an `Active` test if its failure rate over the last 7 days is greater or equal to the specified threshold. The rule is triggered every 15 minutes.</ul> |

[estherk15]

Suggested change

| **Disable** | Toggle to allow flaky tests to be disabled for this repository. You may want to do this after quarantining or to protect specific branches from flakiness. Customize automation rules based on: <li>Status and time: Disable a test if it has a specified status for a specified number of days. The rule is triggered every day at 12:30 UTC. <li>Branch: Disable an `Active` or `Quarantined` test if it flakes in one or more specified branches. <li>Failure rate: Disable an `Active` or `Quarantined` test if its failure rate over the last 7 days is greater or equal to the specified threshold. The rule is triggered every 15 minutes. |

| **Disable** | Toggle to allow flaky tests to be disabled for this repository. You may want to do this after quarantining or to protect specific branches from flakiness. Customize automation rules based on: <li>Status and time: Disable a test if it has a specified status for a specified number of days. The rule is triggered every day at 12:30 UTC. <ul><li>Branch: Disable an `Active` or `Quarantined` test if it flakes in one or more specified branches. <li>Failure rate: Disable an `Active` or `Quarantined` test if its failure rate over the last 7 days is greater or equal to the specified threshold. The rule is triggered every 15 minutes. </ul>|

[TovRudyy]

Left a suggestion to fix the list formatting, but approved!

I opted to refactor the table in HTML. It actually looks better: