remove unused boost-filesystem

[InvincibleRMC]

Description

Removed boost filesystem. Not actually being used anymore and already replaced with std::filesystem throughout.

Checklist

• [x] Required by CI: Code is auto formatted using clang-format
• [x] Extend the tutorials / documentation reference
• [x] Document API changes relevant to the user in the MIGRATION.md notes
• [x] Create tests, which fail without this PR reference
• [x] Include a screenshot if changing a GUI
• [x] While waiting for someone to review your request, please help review another open pull request to support the maintainers