Relaxe upper bounds on some dependencies

[sscherfke]

• The "^" specifier is often too restrictive for 0.* versions so I would not recommend to use it in these cases: https://python-poetry.org/docs/dependency-specification/
• Markdown2: The issue from 2.4.11 was fixed in 2.4.12:
  • Update markdown2 dependency #2154
  • Markdown Syntax Not Converted Within HTML Tags in markdown2 trentm/python-markdown2#546
  • https://github.com/trentm/python-markdown2/blob/master/CHANGES.md#python-markdown2-2412
• Watchfiles: Doesn't look like v1 will introduce breaking changes: Version 1? samuelcolvin/watchfiles#186
• python-multipart: "^0.06" is "==0.0.6" which is too strict and at this stage, any release can potentially add breaking changes
• aiofiles: Uses CalVer and 24.0.0 is as likely to introduce breaking changes as 23.2.0.
• httpx: It does not look like 1.0.0 will introduce breaking changes (if you already fixed any deprecation warnings). Testing against the 1.0.0beata0 is advisable, though. Draft 1.0 release notes encode/httpx#3069
• ifaddr: Development is rather slow, package looks quite stable. I don't think that a 0.3.0 will add breaking changes and a 1.0 is not in sight.
• pytest-asyncio: Restriction to >=0.19,<0.20 seems unwanted and updates are needed for recent pytest versions
• pytest: Has there been a reason to not support pytest7? pytest8 currently breaks some plugins, but this should be fixed soon.

Fixes: #2485

[rodja]

Very nice! Let's merge.