[Merged by Bors] - chore(Geometry/Manifold/Immersion): minor tweaks

[grunweg]

• remove superfluous noncomputable
• golf one proof very slightly
• a few wording improvements to the module doc-string (content-neutral)

Noticed while reviewing #35122.

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[github-actions]

PR summary a8af750656

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/pr_summary/declarations_diff.sh <optional_commit>

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

The doc-module for scripts/pr_summary/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/reporting/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).

[ocfnash]

Thanks!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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