fix: bottom padding on swap modal (#6715)

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## Description
<!-- Summary of change, including motivation and context. -->
<!-- Use verb-driven language: "Fixes XYZ" instead of "This change fixes XYZ" -->


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_Linear ticket:_ https://linear.app/uniswap/issue/WEB-2151/permit2-fix-dialog-window-height


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## Screen capture

### Before
|    Mobile    |   Desktop    |
| ------------ | ------------ |
| paste_before | <img width="516" alt="image" src="https://github.com/Uniswap/interface/assets/66155195/4b7320c3-9bd3-4c5c-8d28-341a5ae7fa4f"> |


### After
|    Mobile    |   Desktop   |
| ------------ | ----------- |
| paste_after  | ![image](https://github.com/Uniswap/interface/assets/66155195/8b112a05-39d5-4a01-b412-47a7d74d040f) |

src/components/swap/PendingModalContent/index.tsx

@@ -27,7 +27,7 @@ import {
 import { TradeSummary } from './TradeSummary'
 
 export const PendingModalContainer = styled(ColumnCenter)`
-  margin: 48px 0 28px;
+  margin: 48px 0 8px;
 `
 
 const HeaderContainer = styled(ColumnCenter)<{ $disabled?: boolean }>`