fix(Alert): height and alignment

### Overview
Two Issues:
1. The Alert's alignments were off (not centered and stretched out):
The alignment Alert wasn't rendering properly because the alert was stretched vertically.
Upon investigation, it was the X button that had a large height, despite the button seemingly set to "small"

Looking into IconButton, seems like the size prop wasn't used, adding this prop back in seemed to fix the issue.
--- 
2. The border radius of both inline and general alerts should be 3px. 

### PR Checklist

- [ ] Related to designs: https://www.figma.com/design/ReGfRNillGABAj5SlITalN/%F0%9F%93%90-Gamut?node-id=30186-40358&m=dev 
- [ ] Related to JIRA ticket: [ABC-123]
- [X] I have run this code to verify it works
- [ ] This PR includes unit tests for the code change
- [ ] This PR includes testing instructions tests for the code change
- [ ] The alpha package of this PR is passing end-to-end tests in all relevant Codecademy repositories

#### Testing Instructions

1. Go to `/docs/molecules-alert--usage-guidelines#alert-types` 
2. Check that the height alignment matches [figma](https://www.figma.com/design/ReGfRNillGABAj5SlITalN/%F0%9F%93%90-Gamut?node-id=30186-40358&m=dev)

#### PR Links and Envs

| Repository   | PR Link                                                  | PR Env                                                   |
| :----------- | :------------------------------------------------------- | :------------------------------------------------------- |
| Monolith     | [Monolith PR](http://www.google.fr/ 'Named link title')  | [Monolith Env](http://www.google.fr/ 'Named link title') |
| Portal       | [Portal Link](codecademy-engineering/mono#6915)  | [Portal Env](http://www.google.fr/ 'Named link title')   |
| Another Repo | [Another Link](http://www.google.fr/ 'Named link title') | [Another Env](http://www.google.fr/ 'Named link title')  |

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packages/gamut/src/Alert/variants.tsx

@@ -43,6 +43,7 @@ export const placementVariants = variant({
   prop: 'placement',
   base: {
     alignItems: 'start',
+    borderRadius: '3px',
     columnGap: { _: 4, xs: 8, sm: 12 },
     display: 'grid',
     maxWidth: `calc(${breakpoints.md} - 4rem)`,
@@ -52,12 +53,10 @@ export const placementVariants = variant({
   variants: {
     inline: {
       border: 'none',
-      borderRadius: '3px',
       py: 8,
     },
     floating: {
       borderColor: 'navy',
-      borderRadius: '5px',
       borderStyle: 'solid',
       borderWidth: '2px',
       py: 4,

packages/gamut/src/Button/IconButton.tsx

@@ -64,6 +64,7 @@ export const IconButton = forwardRef<ButtonBaseElements, IconButtonProps>(
           aria-describedby={tipId}
           aria-label={trueAriaLabel}
           ref={ref}
+          size={size}
           variant={variant}
         >
           <Icon size={iconSize} />