Use read-only access methods for read-only entity operations (#31479)

Another follow-up to #31254

Release Notes:

- N/A

crates/extensions_ui/src/extensions_ui.rs

@@ -447,9 +447,11 @@ impl ExtensionsPage {
 
         let extension_store = ExtensionStore::global(cx);
 
-        let dev_extensions = extension_store.update(cx, |store, _| {
-            store.dev_extensions().cloned().collect::<Vec<_>>()
-        });
+        let dev_extensions = extension_store
+            .read(cx)
+            .dev_extensions()
+            .cloned()
+            .collect::<Vec<_>>();
 
         let remote_extensions = extension_store.update(cx, |store, cx| {
             store.fetch_extensions(search.as_deref(), provides_filter.as_ref(), cx)