[Dependencies] Updating Discord.Net (Discord) to 3.19.0

[github-actions]

Description

Related Issue\Feature

How Has This Been Tested

• All unit tests pass.
• All integration tests pass.
• Manual Testing:

Types of changes

• Docs change
• Refactoring
• Dependency upgrade
• Additional Unit Tests\Integration Tests
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Removed no-longer used code

Deployment Configuration Changes

• Requires deployment configuration changes as specified below and in CHANGELOG.md

Checklist

• There are no Resharper\static code analysis errors anywhere in the solution.
• I have ONLY run a code clean-up on any files I have modified to make sure they are in the correct format and no others.
• I have added tests to cover my changes.
• I have run the code and quickly verified it all works to my satisfaction.
• All new/modified code has sufficient logging to be able to diagnose what is wrong.
• All new and existing tests passed.
• All new/modified public interfaces/classes have are documented with xmldoc comments.
• Unreleased section of CHANGELOG.md has been updated with details of this PR.