Carousel: theme styles can overwrite the carousel styles

### Impacted plugin

Jetpack

### Steps to Reproduce

1. Start with a site that's connected to WordPress.com, and where you've activated the Carousel feature under Jetpack > Settings > Writing
2. Install and activate the Dyad 2 theme from the WordPress.com showcase
3. Create a new post, insert a gallery block, and upload images from Pexels (they will all have extra information like caption and description that will be useful for our tests)
4. Set the gallery settings to link to the attachment page
5. Publish your post
6. View the post, and click an image to open the carousel modal

### A clear and concise description of what you expected to happen.

All the image's metadata should be clearly visible

### What actually happened

Some of the theme's styles overwrite the default Carousel styles, and we end up not being able to see the image caption (when clicking on the i icon at the bottom of the gallery view)

### Browser

_No response_

### Other information

_No response_

### Platform (Simple, Atomic, or both?)

Simple, Atomic, Self-hosted

### Reproducibility

Consistent

### Severity

Some (< 50%)

### Available workarounds?

Yes, difficult to implement

### Workaround details

You can set up your own custom CSS to overwrite the theme styles:

```css
.jp-carousel-photo-info h3 {
color: #fff;
}
```

Reproduce the issue using the listed Jetpack Carousel, Dyad 2 theme, gallery, and attachment-page steps, then inspect the Carousel modal styles against the theme styles. Confirm the fix by verifying that image metadata, including the caption opened with the information icon, is visible without custom CSS.

Written by the indexing model from the issue text.