chore(FundamentalGroupoid): deprecate of/toPath/Arrow

[alreadydone]

which are unnecessary after CategoryTheory.End was made implicit_reducible in #41779.
also fix typos Iff -> iff

---

[github-actions]

PR summary 922921d8b7

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ eq_iff_homotopic
++ fundamentalGroupToMulOpposite_apply_eq_iff
++-- fundamentalGroupToMulOpposite_apply_eq_Iff

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 922921d).

• +3 new declarations
• −0 removed declarations

+FundamentalGroupoid.eq_iff_homotopic
+IsAddQuotientCoveringMap.fundamentalGroupToMulOpposite_apply_eq_iff
+IsQuotientCoveringMap.fundamentalGroupToMulOpposite_apply_eq_iff

---

No changes to strong technical debt.
No changes to weak technical debt.

Current commit 922921d8b7
Reference commit b0df0c4b5c

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!

[joelriou]

It is probably better to wait until #43759 is merged.