chore: fix diamonds in cyclotomic extensions

[riccardobrasca]

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[github-actions]

PR summary 540364d453

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 (regex)

+ instance : IntCast (CyclotomicField n K)
+ isCyclotomicExtension_of_charZero
- instance [CharZero K] : IsCyclotomicExtension {n} K (CyclotomicField n K)

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

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

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 540364d).

• +2 new declarations
• −1 removed declarations

+CyclotomicField.instIntCast
-CyclotomicField.instIsCyclotomicExtensionSingletonNatSetOfCharZero
+CyclotomicField.isCyclotomicExtension_of_charZero

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Decrease in strong tech debt: (relative, absolute) = (1.00, 0.00)

Current number	Change	Type (strong)
backward.isDefEq.respectTransparency	4351	-1

No changes to weak technical debt.

Current commit 540364d453
Reference commit a8db657b9f

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.py 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).

[github-actions]

✅ PR Title Formatted Correctly

The title of this PR has been updated to match our commit style conventions.
Thank you!