Trigger gem update GHA periodically

Instead of concentrating gem dep updates right before release, we should set up a trigger to update active branches (perhaps weekly). This will help us get more soak time for new gem deps and reduce change set right before release. We can still do a manual run on FF to make sure we are getting the latest, but having gem updates happening at a regular cadence should reduce that change set. This can likely be accomplished by setting up a workflow dispatch for a schedule. Ideally we can automatically determine the streams to be actively managed. If there is a manual step there we should include updating that schedule in the minor release ticket template.

Start by reviewing the existing gem update workflow and the minor release ticket template. Determine how active branches or streams are identified, then define the scheduled workflow and any manual step needed; done means active branches receive periodic gem updates without relying on pre-release runs.

Written by the indexing model from the issue text.