fix: Use margin instead of padding for the Snaps UI Container (#29385)

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## **Description**

Use `margin` instead of `padding` for the Snaps UI Container. This fixes
an issue where using certain components (such as Section) at the root
would look weird.

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## **Screenshots/Recordings**

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before and after of your change. -->

### **Before**


![image](https://github.com/user-attachments/assets/ba7950e6-d41a-411d-aba1-a156a74efaad)


### **After**


![image](https://github.com/user-attachments/assets/c7e475d4-8b61-4ec9-ac55-084c0bb8e2df)

ui/components/app/snaps/snap-ui-renderer/index.scss

@@ -12,14 +12,10 @@
   &__container {
     & > *:first-child {
       gap: 16px;
-      padding: 16px;
+      margin: 16px;
     }
   }
 
-  &__error {
-    margin-top: 0 !important;
-  }
-
   &__spinner {
     width: 30px;
   }