[ThreatMatch] Added Beautifulsoup parsing and cleaned up code

[pietrocapece]

Proposed changes

• Added HTML parsing of the content of alerts with Beautifulsoup
• Removed some legacy code that was commented out

Related issues

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality using different use cases
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[flavienSindou]

@pietrocapece Thank you for the feature addition and for cleaning up the code!

I noticed that the requirements file needs to be updated to resolve the merge conflict. Once that's done, I’ll be happy to approve your pull request.