Related posts block thumbnails appears slightly distorted in some viewport widths

### Quick summary

The featured image block crops the images automatically to be 350px wide by 200px tall (1.75:1 ratio).

However, in some specific viewport widths the images appear slightly distorted:

https://github.com/Automattic/wp-calypso/assets/4965723/b0618fc5-5840-4027-9e88-9cce82374379

### Steps to reproduce

1. Activate Payton.
2. Add a Related Posts block to the Single template.
3. Visit a post.
4. Use the browser developer tools to see the mobile view. Set it to responsive.
5. Adjust the viewport width until you see a distortion in the thumbnails.

### What you expected to happen

The image should not be distorted regarding of the screen size.

### What actually happened

Thumbnails are slightly distorted in some viewport widhts.

### Impact

One

### Available workarounds?

Yes, easy to implement

### Platform (Simple and/or Atomic)

_No response_

### Logs or notes

Context: 6363582-zd-woothemes

Workaround (tested in Payton):

/* Set height for featured images in Related Posts block */

.jp-related-posts-i2__post-img-link img {
height:100%;
}

Start by reproducing the Related Posts block in the Single template with Payton at responsive viewport widths, then inspect the featured-image markup and styles, including the .jp-related-posts-i2__post-img-link img selector. Done means thumbnails keep their intended proportions without distortion across the affected widths.

Written by the indexing model from the issue text.