Add tox -e cog to update README tables

[hugovk]

Also output the tables in GitHub-flavoured Markdown instead of RST, because it's README.md.

And remove the irrelevant Travis CI column, we've not used it for years and .travis.yml was deleted in 2021: python/cpython#30257

[hugovk]

We can't use 3.14 yet because one transitive dependency is pydantic, which doesn't yet support 3.14.

They added initial support in pydantic/pydantic#11613 and have released an alpha, but we're waiting for a final release of pydantic 2.12.

[AA-Turner]

This is a rather heavy dependency for an infrequent task that isn't that much of a hardship:

cog v0.16.6
├── attrs v23.2.0
├── fastapi v0.115.14
│   ├── pydantic v2.11.7
│   │   ├── annotated-types v0.7.0
│   │   ├── pydantic-core v2.33.2
│   │   │   └── typing-extensions v4.15.0
│   │   ├── typing-extensions v4.15.0
│   │   └── typing-inspection v0.4.1
│   │       └── typing-extensions v4.15.0
│   ├── starlette v0.46.2
│   │   └── anyio v4.10.0
│   │       ├── idna v3.10
│   │       └── sniffio v1.3.1
│   └── typing-extensions v4.15.0
├── pydantic v2.11.7 (*)
├── pyyaml v6.0.2
├── requests v2.32.5
│   ├── certifi v2025.8.3
│   ├── charset-normalizer v3.4.3
│   ├── idna v3.10
│   └── urllib3 v2.5.0
├── structlog v24.4.0
├── typing-extensions v4.15.0
└── uvicorn v0.35.0
    ├── click v8.2.1
    │   └── colorama v0.4.6
    └── h11 v0.16.0

I'd be fine with using GFM tables (though they're rather verbose in the source), but I don't think we need the other changes in this PR.

A

[hugovk]

Good point, I've moved the cog dependency out of tools_requirements.txt, so it's only installed when running tox.