settings: Remove unused stream_edits setting in agent (#40640)

This setting is unused (we always stream edits)

Release Notes:

- N/A

assets/settings/default.json

@@ -884,8 +884,6 @@
     // Note: This setting has no effect on external agents that support permission modes, such as Claude Code.
     //       You can set `agent_servers.claude.default_mode` to `bypassPermissions` to skip all permission requests.
     "always_allow_tool_actions": false,
-    // When enabled, the agent will stream edits.
-    "stream_edits": false,
     // When enabled, agent edits will be displayed in single-file editors for review
     "single_file_review": true,
     // When enabled, show voting thumbs for feedback on agent edits.