Fix Certbot installation in gromox-core Dockerfile for Let's Encrypt support

[simialfapro]

Description
Currently, the gromox-core/Dockerfile installs Certbot using the packages:

python3-certbot python3-certbot-nginx

This does not properly install Certbot on newer openSUSE bases, preventing automatic issuance of Let's Encrypt certificates.

Proposed Change

Replace the current Certbot installation in the Dockerfile:

RUN zypper --non-interactive install -y vim mysql \
    gromox grommunio-admin-api grommunio-admin-web grommunio-antispam \
    grommunio-common grommunio-web grommunio-sync grommunio-dav postfix postfix-mysql \  
    grommunio-chat firewalld cyrus-sasl-saslauthd cyrus-sasl-plain jq \
    python3-certbot python3-certbot-nginx

with a Python 3.11-based installation:

RUN    zypper --non-interactive install -y vim mysql        \
	gromox grommunio-admin-api grommunio-admin-web grommunio-antispam \
	grommunio-common grommunio-web grommunio-sync grommunio-dav postfix postfix-mysql \  
	grommunio-chat firewalld cyrus-sasl-saslauthd cyrus-sasl-plain jq redis

# Install Certbot & dependencies (Python 3.11)
RUN zypper -n install -y python311 python311-pip libopenssl-devel && \
    pip3.11 install --no-cache-dir certbot certbot-nginx && \
    ln -sf /usr/local/bin/certbot /usr/bin/certbot

This ensures:

• Certbot is correctly installed with Python 3.11
• certbot CLI works as expected
• Automatic issuance of Let's Encrypt certificates is possible

Without this change, users are unable to request or renew Let's Encrypt certificates inside the container.
Updating the Dockerfile will make Grommunio fully compatible with Let's Encrypt setups.