UPDATE 06/2021: The latest version of phpmyadmin image from Docker includes an UPLOAD_LIMIT attribute you can add to your docker-compose file, so I would recommend doing that instead. I don't believe this works with the newer versions of phpmyadmin, but I'll leave it here for posterity.
I found several articles regarding upping the upload_max_filesize and post_max_size for PHP for PHPMyAdmin, but I don't believe they consider the phpmyadmin Docker image. Since this is separate from the WordPress image that I use, it doesn't utilize the same php.ini file that we're using to adjust these numbers.
It's a pretty straightforward fix and should utilize the same file you're currently using for your php.ini override. In this instance, we're using uploads.ini as our override file.
The difference from other docker-compose files is that I'm specifying the phpmyadmin image to also utilize the uploads.ini file that's overriding our php.ini values. Adding this line will apply your values that you're using