docs: Fix project_panel setting defaults (zed-industries#15358)

This PR fixes the defaults for the `project_panel` setting shown in the
docs.

Release Notes:

- N/A

docs/src/configuring-zed.md

@@ -1569,20 +1569,22 @@ Run the `theme selector: toggle` action in the command palette to see a current
 - Default:
 
 ```json
-"project_panel": {
-  "button": true,
-  "dock": "left",
-  "git_status": true,
-  "default_width": "N/A - width in pixels",
-  "auto_reveal_entries": true,
-  "auto_fold_dirs": false,
-  "file_icons": true,
-  "folder_icons": true,
-  "indent_size" : 20,
-  "scrollbar": {
-    "show": "always"
+{
+  "project_panel": {
+    "button": true,
+    "default_width": 240,
+    "dock": "left",
+    "file_icons": true,
+    "folder_icons": true,
+    "git_status": true,
+    "indent_size": 20,
+    "auto_reveal_entries": true,
+    "auto_fold_dirs": true,
+    "scrollbar": {
+      "show": "always"
+    }
   }
-},
+}
 ```
 
 ### Dock