After running "apt update && apt dist-upgrade" selected "Y" to the following:

Configuration file '/etc/php/7.3/fpm/pool.d/www.conf'
==> Modified (by you or by a script) since installation.
==> Package distributor has shipped an updated version.
   What would you like to do about it ?  Your options are:
    Y or I  : install the package maintainer's version
    N or O  : keep your currently-installed version
      D     : show the differences between the versions
      Z     : start a shell to examine the situation

Was a mistake made and does something need to fixed now?

I will answer my own question. Yes a mistake was made because Roundcube is now giving a 502 Bad Gateway error. iRedAdmin login still works.

Resolved the issue by restoring www.conf.dpkg-old.

So if prompted for the above click "N" keeping the currently installed version.

==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.40
- Deployed with iRedMail Easy or the downloadable installer? No
- Linux/BSD distribution name and version: Debian 10
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====