[Merged by Bors] - chore: enable assert_not_exists in BigOperators

[Ruben-VandeVelde]

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[github-actions]

PR summary d306471d9a

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[YaelDillies]

🎉

maintainer merge

[github-actions]

🚀 Pull request has been placed on the maintainer queue by YaelDillies.

[ocfnash]

@YaelDillies Can you give some more context here? It looks like this was dropped in #23897?

[YaelDillies]

These commented-out assert_not_existss were added by me in #11750 while I was untangling the Algebra, Data and Order folders. They couldn't be uncommented at the time because the multiset library imported basic algebraic order theory. I don't know what exactly has made it possibly to uncomment them now, I didn't think it was (even close to) solved yet. Probably the module system? I don't see what #23897 has to do with anything, it merely split one of the files containing a commented-out assert_not_exists.

[j-loreaux]

I don't see any reason not to merge.

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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