chore: Bump mathlib dependency to 6727686 (#527)

Bump `mathlib` dependency to
[6727686](leanprover-community/mathlib4@6727686):
ci(olean_report): use `lake env` instead of `lake exec` to invoke cache
binary (#38712) (2026-04-29)
Previously at:
[2d59066](leanprover-community/mathlib4@2d59066):
refactor(Data/Matrix): protect `Matrix.mul_smul` (#38570) (2026-04-27)

_This PR was last updated on 2026-05-01 by [this workflow
run](https://github.com/leanprover/cslib/actions/runs/25231473662). It
is an automated bump using
[downstream-reports/open-bump-pr](https://github.com/leanprover-community/downstream-reports)_

---------

Co-authored-by: mathlib-nightly-testing[bot] <mathlib-nightly-testing[bot]@users.noreply.github.com>
Co-authored-by: Chris Henson <chrishenson.net@gmail.com>

Author: mathlib-nightly-testing[bot]

Cslib/Logics/Propositional/NaturalDeduction/Basic.lean

@@ -11,8 +11,6 @@ public import Mathlib.Data.Finset.Insert
 public import Mathlib.Data.Finset.SDiff
 public import Mathlib.Data.Finset.Image
 
-@[expose] public section
-
 /-! # Natural deduction for propositional logic
 
 We define, for minimal logic, deduction trees (a `Type`) and derivability (a `Prop`) relative to a
@@ -61,6 +59,8 @@ in §2.2 of Sorensen & Urzyczyn's *Lectures on the Curry-Howard Isomorphism*. (S
 references welcome!)
 -/
 
+@[expose] public section
+
 universe u
 
 namespace Cslib.Logic.PL

lake-manifest.json

@@ -5,10 +5,10 @@
    "type": "git",
    "subDir": null,
    "scope": "leanprover-community",
-   "rev": "2d59066e04cb90e9fa4d1393a8cd1ee8ace8daa7",
+   "rev": "672768680fb7e4eff7dac7ceca12bc3889fd60fd",
    "name": "mathlib",
    "manifestFile": "lake-manifest.json",
-   "inputRev": "master",
+   "inputRev": "672768680fb7e4eff7dac7ceca12bc3889fd60fd",
    "inherited": false,
    "configFile": "lakefile.lean"},
   {"url": "https://github.com/leanprover-community/plausible",

lakefile.toml

@@ -18,6 +18,7 @@ weak.linter.unicodeLinter = false
 [[require]]
 name = "mathlib"
 scope = "leanprover-community"
+rev = "672768680fb7e4eff7dac7ceca12bc3889fd60fd"
 
 [[lean_lib]]
 name = "Cslib"
@@ -26,6 +27,7 @@ globs = ["Cslib.*"]
 [[lean_lib]]
 name = "CslibTests"
 globs = ["CslibTests.+"]
+moreLeanArgs = ["-Dweak.linter.style.header=false"]
 
 [[lean_exe]]
 name = "checkInitImports"