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/begin.mdx

@@ -1,6 +1,9 @@
 ---
 sidebar_position: 1
 slug: /begin_component
+sidebar_custom_props: {
+  categoryIcon: LucideHome
+}
 ---
 
 # Begin component
@@ -36,9 +39,9 @@ An agent in conversational mode begins with an opening greeting. It is the agent
 
 You can define global variables within the **Begin** component, which can be either mandatory or optional. Once set, users will need to provide values for these variables when engaging with the agent. Click **+ Add variable** to add a global variable, each with the following attributes:
 
-- **Name**: _Required_  
-  A descriptive name providing additional details about the variable.  
-- **Type**: _Required_  
+- **Name**: _Required_
+  A descriptive name providing additional details about the variable.
+- **Type**: _Required_
   The type of the variable:
   - **Single-line text**: Accepts a single line of text without line breaks.
   - **Paragraph text**: Accepts multiple lines of text, including line breaks.
@@ -46,7 +49,7 @@ You can define global variables within the **Begin** component, which can be eit
   - **file upload**: Requires the user to upload one or multiple files.
   - **Number**: Accepts a number as input.
   - **Boolean**: Requires the user to toggle between on and off.
-- **Key**: _Required_  
+- **Key**: _Required_
   The unique variable name.
 - **Optional**: A toggle indicating whether the variable is optional.