Due to OS version detection, ubuntu and debian are detected as linux, limiting maximum the version of mongo to 4.0

[rdar-lab]

Describe the bug
The OS detection will detect ubuntu and debian as 'linux'
As such the URLS for download will be limited to a maximum of version 4.0

To Reproduce
Steps to reproduce the behavior:

1. Use ubuntu server/desktop
2. Try to set the version using env variables to 6.0
3. Run with pymongo_inmemory
4. Check Mongo server version. It will be 4.0

Expected behavior
Version 6.0 should be installed

Logs
Not applicable

Screenshots
Not applicable

Context:

• OS: Ubuntu 22.04
• Version of pymongo_inmemory: 0.4.2

[rdar-lab]

PR for a fix:
#114