Change default port for registry to avoid conflict with macOS Control Center

Overview

@cwoolley-gitlab and @jeldergl reported in Slack that the default port for the registry (5000) conflicts with macOS Control Center. This forces macOS users to manually change their port in GDK.

We should pick a different default port for the registry to fix this problem.

Impacted categories

The following categories relate to this issue:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Steps to replicate (optional)

Proposal (optional)

Environment (optional)

• Operating system name: <!-- output of `uname -a` command -->
• Architecture: <!-- output of `arch` or `uname -m` command -->
• The contents of your gdk.yml (if any)
• Ruby version: <!-- output of `ruby --version` command -->
• GDK version: <!-- output of `git rev-parse --short HEAD` command -->