Update InnerBlocks defaultblock doc usage (#56728)

Co-authored-by: Riad Benguella <benguella@gmail.com>

packages/block-editor/src/components/inner-blocks/README.md

@@ -188,8 +188,19 @@ For example, a button block, deeply nested in several levels of block `X` that u
 
 ### `defaultBlock`
 
-- **Type:** `Array`
-- **Default:** - `undefined`. Determines which block type should be inserted by default and any attributes that should be set by default when the block is inserted. Takes an array in the form of `[ blockname, {blockAttributes} ]`.
+- **Type:** `Object`
+- **Default:** - `undefined`
+
+Determines which block type should be inserted by default and any attributes that should be set by default when the block is inserted. Takes an object in the form of `{ name: blockname, attributes: {blockAttributes} }`.
+
+```jsx
+const DEFAULT_BLOCK = { name: 'core/paragraph', attributes: { content: 'Lorem ipsum...' } };
+...
+<InnerBlocks
+    defaultBlock={ DEFAULT_BLOCK }
+    directInsert={ true }
+/>
+```
 
 ### `directInsert`