docs: Correct minimum FastAPI version for lifespan handling

[tim-hutchinson]

Description

Based on the git blame and #1736, I believe the minimum version of FastAPI for handling lifespan functions correctly is 112.2, not 102.2. Just ran into this trying to work out why our broker was never getting connected on an older (103) FastAPI install.

Type of change

Please delete options that are not relevant.

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• My code adheres to the style guidelines of this project (scripts/lint.sh shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment by running scripts/test-cov.sh
• I have ensured that static analysis tests are passing by running scripts/static-analysis.sh
• I have included code examples to illustrate the modifications

[Lancetnik]

Thank you for the notice and PR a lot!