feat: replace probably erroneous usage of ⬝ (with old \cdot) by · (with \centerdot)

[MoritzBeroRoos]

Discussion at zulip.

Currently the abbreviations \cdot and \centerdot resolve to different, with the naked eye nearly undistinguishable symbols (despite the c in cdot surely standing for center..).

This pr replaces instances of ⬝ where · was probably meant.
All of the replacement is in comments, except for the file bench_summary.lean which is used for priting the github benchmark results. Since this file is about scientific notation of numbers, sure · was meant to be used, not a rectangle.

Related

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[github-actions]

PR summary d3c295b45d

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).

[eric-wieser]

Could you revert these dotProduct changes to make the PR orthogonal? you can just find and replace this digraph back with the original