fix: updated margin for import token banner (#29283)

This PR is to update the margin bottom in the detected token banner

## **Description**

This PR updates the Top right bottom and left margin to 16px, 16px, 4px
and 16px for import token banner

## **Related issues**

Fixes: #26670 

## **Manual testing steps**

1. Must be a new user with not all tokens added
2. Open MetaMask
3. If user has detected tokens, check the margin of the banner

## **Screenshots/Recordings**


### **Before**
![Screenshot 2024-12-17 at 3 06
39 PM](https://github.com/user-attachments/assets/b912aa7a-04da-4354-88bc-c37ca4433b25)


### **After**
![Screenshot 2024-12-17 at 3 38
33 PM](https://github.com/user-attachments/assets/b7d4afba-615a-4df3-8598-ef2b82d18143)


## **Pre-merge author checklist**

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

ui/components/app/assets/asset-list/asset-list.tsx

@@ -127,6 +127,7 @@ const AssetList = ({ onClickAsset, showTokensLinks }: AssetListProps) => {
           className=""
           actionButtonOnClick={() => setShowDetectedTokens(true)}
           margin={4}
+          marginBottom={1}
         />
       ) : null}
       <AssetListControlBar showTokensLinks={shouldShowTokensLinks} />