docs: remove Editor Plugins section and fold RPC into Web Servers

Remove the Editor Plugins and IDEs section — modern editors handle Python
via LSP natively, making a curated list of editor plugins less useful.

Consolidate the standalone RPC Servers section into a subsection under
Web Servers to reflect that grpcio and rpyc are network server libraries,
not a separate category.

Co-Authored-By: Claude <[email protected]>