docs: update docs icons (#12465)

### What problem does this PR solve?

Update icons for docs.
Trailing spaces are auto truncated by the editor, does not affect real
content.

### Type of change

- [x] Documentation Update

docs/guides/agent/agent_component_reference/retrieval.mdx

@@ -1,6 +1,9 @@
 ---
 sidebar_position: 3
 slug: /retrieval_component
+sidebar_custom_props: {
+  categoryIcon: LucideFolderSearch
+}
 ---
 
 # Retrieval component
@@ -21,13 +24,13 @@ Ensure you [have properly configured your target dataset(s)](../../dataset/confi
 
 ## Quickstart
 
-### 1. Click on a **Retrieval** component to show its configuration panel  
+### 1. Click on a **Retrieval** component to show its configuration panel
 
 The corresponding configuration panel appears to the right of the canvas. Use this panel to define and fine-tune the **Retrieval** component's search behavior.
 
 ### 2. Input query variable(s)
 
-The **Retrieval** component depends on query variables to specify its queries. 
+The **Retrieval** component depends on query variables to specify its queries.
 
 :::caution IMPORTANT
 - If you use the **Retrieval** component as a standalone workflow module, input query variables in the **Input Variables** text box.
@@ -74,7 +77,7 @@ Select the query source for retrieval. Defaults to `sys.query`, which is the def
 
 The **Retrieval** component relies on query variables to specify its queries. All global variables defined before the **Retrieval** component can also be used as queries. Use the `(x)` button or type `/` to show all the available query variables.
 
-### Knowledge bases 
+### Knowledge bases
 
 Select the dataset(s) to retrieve data from.
 
@@ -110,7 +113,7 @@ Using a rerank model will *significantly* increase the system's response time.
 
 ### Empty response
 
-- Set this as a response if no results are retrieved from the dataset(s) for your query, or 
+- Set this as a response if no results are retrieved from the dataset(s) for your query, or
 - Leave this field blank to allow the chat model to improvise when nothing is found.
 
 :::caution WARNING