net-mgmt/netbox: Update to 4.6.3

• Remove no longer required workarounds for Python 3.11 compatibility.

• Also prune update instructions for NetBox releases older than 3.6 while I'm here.

Netbox 4.6 contains many bugfixes/enhancements and the following new
features:

• Virtual Machine Types
• Cable Bundles
• Rack Groups
• ETag Support for REST API
• Cursor-based Pagination for REST API

https://netbox.readthedocs.io/en/stable/release-notes/version-4.6/

MFH: No (feature release)