assistant_context_editor: Remove suggest edits (#30286)

This PR removes the code for the "Suggest Edits" functionality from
Assistant1.

This feature was already disabled entirely with the launch of the Agent,
we're just cleaning up the unused code.

Release Notes:

- N/A

docs/src/ai/text-threads.md

@@ -228,7 +228,6 @@ Zed has the following internal rule templates:
 
 - `content_prompt.hbs`: Used for generating content in the editor.
 - `terminal_assistant_prompt.hbs`: Used for the terminal assistant feature.
-- `suggest_edits.hbs`: Used for generating the model instructions for the XML Suggest Edits should return.
 
 At this point it is unknown if we will expand templates further to be user-creatable.
 
@@ -244,8 +243,6 @@ The following templates can be overridden:
 
 2. [`terminal_assistant_prompt.hbs`](https://github.com/zed-industries/zed/tree/main/assets/prompts/terminal_assistant_prompt.hbs): Used for the terminal assistant feature.
 
-3. [`suggest_edits.hbs`](https://github.com/zed-industries/zed/tree/main/assets/prompts/suggest_edits.hbs): Used for generating the model instructions for the XML Suggest Edits should return.
-
 > **Note:** Be sure you want to override these, as you'll miss out on iteration on our built-in features. This should be primarily used when developing Zed.
 
 You can customize these templates to better suit your needs while maintaining the core structure and variables used by Zed. Zed will automatically reload your prompt overrides when they change on disk.