Clean up integration-docs-platforms

[matejminar]

Once the profiling and replay docs are moved over to the sentry repo, we can do a cleanup of integration-docs-platforms. That would include:

• Webpack configuration that sets up this integration-docs-platforms alias
• Webpack plugin to download
• Python implementation to download

See https://github.com/getsentry/sentry/pull/54678/files#r1293806721

[ArthurKnaus]

I checked the current implementation, there is no webpack plugin anymore. However, there is a different mechanism now. What remains to do is:

1. Remove / Migrate Inline docs that are shown in the trace view for spans that are missing instrumentation.
2. Remove the build-platform-assets build step that downloads the docs on backend build (see _integration_docs.py)
3. Remove ProjectDocsPlatformEndpoint