Update user-facing error messages that refer to Slack channels to now refer to #dlss-aaas

[andrewjbtw]

There are a number of user-facing error messages that appear in Argo banner messages. Some of these suggest that the user contact a Slack channel for assistance. We have not been consistent on which Slack channel to contact for various reasons, including a lack of a central SDR support channel, changing contexts of work, and so on.

Since these banner messages are meant for Argo users (unlike HB messages), and since the #dlss-aaas channel has become the de facto SDR support channel (not just for accessioning), we should update all messages to refer to that channel.

A couple of channels that have been put into error messages in the past that we should no longer use:

• #sdr-operations - this was created around the time I started and never gained traction. It's still around but basically it's just me and Tony C. and Tony Z. We used to have to do much more operational support (remediation of errors, etc.)
• #dlss-infrastructure - this is too dev-focused for Argo messages. Especially as we get further from the Fedora migration, issues that show up in Argo are less likely to directly involve the dev team.