settings: Remove version fields (#33372)

This cleans up our settings to not include any `version` fields, as we
have an actual settings migrator now.

This PR removes `language_models > anthropic > version`,
`language_models > openai > version` and `agent > version`.

We had migration paths in the code for a long time, so in practice
almost everyone should be using the latest version of these settings.


Release Notes:

- Remove `version` fields in settings for `agent`, `language_models >
anthropic`, `language_models > openai`. Your settings will automatically
be migrated. If you're running into issues with this open an issue
[here](https://github.com/zed-industries/zed/issues)

crates/zed/src/zed.rs

@@ -4441,12 +4441,7 @@ mod tests {
             );
             image_viewer::init(cx);
             language_model::init(app_state.client.clone(), cx);
-            language_models::init(
-                app_state.user_store.clone(),
-                app_state.client.clone(),
-                app_state.fs.clone(),
-                cx,
-            );
+            language_models::init(app_state.user_store.clone(), app_state.client.clone(), cx);
             web_search::init(cx);
             web_search_providers::init(app_state.client.clone(), cx);
             let prompt_builder = PromptBuilder::load(app_state.fs.clone(), false, cx);