Fix team members listing for Reliability:General and Reliability:Observability

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@dawsmith is the permanent team lead for Reliability:Observability and also the acting team lead for Reliability:General following Anthony's departure. We use the method direct_team() to build the table of team members with the parameter manager_slug: 'dave-smith'. Because Dave is the current lead for both teams, both the observability and general pages end up with the same team member listing, which is not ideal.

I've updated the direct_team() method to accept an optional department parameter. If specified, the team members have to match on the department. This MR also updates each of the team members to list either Reliability:General or Reliability:Observability as a department.

This MR supersedes !130437 (closed).

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