Use w-auto instead of object-contain (#3230)

## Description

There was a bug in #3228 that caused the placeholder to be larger than
the image. For some reason, the dev preview does not show the blurred
placeholder.

left is dev, right is after static site generation (SSG). 

<img width="2672" alt="image"
src="https://github.com/user-attachments/assets/d16f48b8-a6e7-4b45-9a1c-667c0f01240f">

This PR fixes this by adding `w-auto`. This will automatically resize
the width to maintain aspect ratio with the height. Because of this, we
can remove object-contain. object-contain was used to prevent image
stretching.

Before/after:
<img width="2531" alt="image"
src="https://github.com/user-attachments/assets/c50defd3-09d1-4763-a63e-9e77658afc7d">

## Checklist
- [x] I have read and understood the [WATcloud
Guidelines](https://cloud.watonomous.ca/docs/community-docs/watcloud/guidelines)
- [x] I have performed a self-review of my code

components/blog-post.tsx

@@ -112,7 +112,7 @@ export function BlogPostHeader() {
                     <Picture
                         image={titleImage}
                         alt={titleImageAttribution}
-                        imgClassName='max-h-96 object-contain'
+                        imgClassName='max-h-96 w-auto'
                     />
                 </PopoverTrigger>
                 <PopoverContent side='bottom' className="w-96 max-w-full">