Remove any documentation from the repo other than API reference

[bruno-garcia]

Only the API reference should live on gh-pages, all docs are done on docs.sentry.io.

• Remove any documentation (such as the log4net docs) and point to docs.sentry.io
• Let the API reference point to the latest released package. For that, the docs workflow should only trigger when a tag is pushed instead of each merge to main. Seems not to be working (https://github.com/getsentry/sentry-dotnet/actions/workflows/docs.yml)
• Workflow to change: https://github.com/getsentry/sentry-dotnet/blob/2d6c847268c9422c0a02bffe87dd656736cf197c/.github/workflows/docs.yml#L3-L6