Remove merge queue support from CI workflows

[daimon-pymclabs]

Drops the merge_group: trigger from test.yml, test_notebook.yml, pypi.yml, and docs.yml so CI no longer runs in merge-queue context.

This PR alone does not disable the merge queue. The queue is a branch-protection setting on main, not a file in the repo, so it has to be turned off in the repo settings ("Require merge queue" under the main protection rule).

Order matters: turn the setting off first, then merge this. If the workflows lose their merge_group triggers while the queue is still required, the required checks (all_tests, build source distribution check) never report in queue context and every entry stalls until it times out. There are 3 PRs in the queue right now.

🤖 Generated with Claude Code

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📚 Documentation preview 📚: https://pymc-marketing--2786.org.readthedocs.build/en/2786/

[cursor]

PR Summary

Medium Risk
Merge timing matters: if branch protection still requires the merge queue while these triggers are gone, required checks may not run in queue context and merges can stall until the queue setting is disabled first.

Overview
Stops running CI on GitHub merge-queue events by deleting the merge_group: trigger from test.yml, docs.yml, pypi.yml, and test_notebook.yml. Those workflows still run on pull_request and push to main and v1.0.0 (plus release events on PyPI).

In test_notebook.yml, the duplicate merge_group block that mirrored the same path filters as pull_request/push is removed entirely—no other job or step logic changes.

^{Reviewed by Cursor Bugbot for commit ef35bcd. Bugbot is set up for automated code reviews on this repo. Configure here.}

[juanitorduz]

@williambdean do you also want to remove this from the branch rule?

[daimon-pymclabs]

@juanitorduz yes — and it has to come first, not after. The branch rule is the half of this that isn't in code, and Bugbot's medium-risk note above is the same point: while "Require merge queue" is still on for main, dropping the merge_group: triggers means a queued PR builds a gh-readonly-queue/... ref that no workflow reacts to, so all_tests and build source distribution check never report in queue context and the entry sits there until it times out.

The queue is definitely still live, so this isn't hypothetical — #2773 ran Test/Docs/PyPI on gh-readonly-queue/main/pr-2773-8de81b8 at 07:30 today, and #2770 was merged by github-merge-queue[bot] at 07:42.

So the order is: turn off "Require merge queue" on the main branch rule (and v1.0.0 if it's set there too), let the queue drain, then merge this. I don't have admin on the repo so I can't flip the setting — @williambdean or you would need to. Happy to leave this PR sitting until that's done.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.32%. Comparing base (7e1ac23) to head (ef35bcd).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2786   +/-   ##
=======================================
  Coverage   94.32%   94.32%           
=======================================
  Files         102      102           
  Lines       15616    15616           
=======================================
  Hits        14730    14730           
  Misses        886      886           

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