Edit Predictions: without ZED_PREDICT_EDITS_URL cannot set local backend

[phromo]

Summary

Recently ZED_PREDICT_EDITS_URL was removed. The removal makes it very difficult to use a custom edit prediction backend.

Description

A few hours ago in #30290 the feature to use ZED_PREDICT_EDITS_URL was removed. It now becomes unnecessary complicated to set a custom URL. Implementing a backend handling the EditPredict api has already been made by the community, see for instance https://github.com/praktiskt/zedex/blob/cdeda38fb5a93e64e43c1587d27b782c59cd6ca7/src/zed/edit_predict.go#L28 -- but now one must forego zed logon to use it.

Previously I could just use any custom edit predict backend, including Zeta-based backend.

Actual Behavior: No way to set edit predict url. Expected Behavior: Could set ZED_PREDICT_EDITS_URL like before #30290

Zed Version and System Specs

Zed: v0.184.5 (Zed Preview) OS: Linux X11 ubuntu 24.04 Memory: 62.5 GiB Architecture: x86_64 GPU: Intel(R) Graphics (RPL-S) || Intel open-source Mesa driver || Mesa 24.2.8-1ubuntu1~24.04.1