Patch update streaming docs

[tkatsoulas]

Summary

There are two (overlapping) sections in our docs about Agent streaming components.

1. https://github.com/netdata/netdata/blob/master/streaming/README.md
2. https://github.com/netdata/netdata/tree/master/docs/metrics-storage-management

This PR obsoletes (but not deletes) the streaming/README.md doc, every update should be made on https://github.com/netdata/netdata/tree/master/docs/metrics-storage-management docs which are part of the learn's TOC tree.

Test Plan

Part of learn