doc(Algebra): fix file refs (leanprover-community#33620)

Update some stale file references.

Author: harahu

Mathlib/Algebra/Group/Subsemigroup/Operations.lean

@@ -56,8 +56,8 @@ In this file we define various operations on `Subsemigroup`s and `MulHom`s.
 
 ### Implementation notes
 
-This file follows closely `GroupTheory/Submonoid/Operations.lean`, omitting only that which is
-necessary.
+This file follows closely `Mathlib/Algebra/Group/Submonoid/Operations.lean`, omitting only that
+which is necessary.
 
 ## Tags
 

Mathlib/Algebra/Group/Units/Defs.lean

@@ -18,7 +18,8 @@ An element of a `Monoid` is a unit if it has a two-sided inverse.
 * `IsUnit x`: a predicate asserting that `x` is a unit (i.e., invertible element) of a monoid.
 
 For both declarations, there is an additive counterpart: `AddUnits` and `IsAddUnit`.
-See also `Prime`, `Associated`, and `Irreducible` in `Mathlib/Algebra/Associated.lean`.
+See also `Prime`, `Associated`, and `Irreducible` in
+`Mathlib/Algebra/GroupWithZero/Associated.lean`.
 
 ## Notation
 

Mathlib/Algebra/HierarchyDesign.lean

@@ -101,12 +101,13 @@ when applicable:
   instance Finsupp.Z [Z β] : Z (α →₀ β) := ...
   ```
 * Instances transferred elementwise to `Set`s, like `Set.monoid`.
-  See `Mathlib/Algebra/Pointwise.lean` for more examples.
+  See `Mathlib/Algebra/Group/Pointwise/Set/Basic.lean` for more examples.
   ```
   instance Set.Z [Z α] : Z (Set α) := ...
   ```
 * Definitions for transferring the entire structure across an equivalence, like `Equiv.monoid`.
-  See `Mathlib/Data/Equiv/TransferInstance.lean` for more examples. See also the `transport` tactic.
+  See `Mathlib/Algebra/Group/TransferInstance.lean` for more examples. See also the `transport`
+  tactic.
   ```
   def Equiv.Z (e : α ≃ β) [Z β] : Z α := ...
   /-- When there is a new notion of `Z`-equiv: -/

Mathlib/Algebra/Module/Presentation/Differentials.lean

@@ -28,7 +28,7 @@ The main result in this file is that `Ω[S⁄R]` identifies to the quotient of t
 free `S`-module on `ι` by the submodule generated by these
 elements `pres.differentialsRelations.relation r`. We show this as a consequence
 of `Algebra.Extension.exact_cotangentComplex_toKaehler`
-from the file `Mathlib/RingTheory/Kaehler/CotangentComplex.lean`.
+from the file `Mathlib/RingTheory/Extension/Cotangent/Basic.lean`.
 
 -/
 

Mathlib/Algebra/Ring/Action/End.lean

@@ -20,7 +20,7 @@ multiplication in `Equiv.Perm`, and multiplication in `CategoryTheory.End`, but
 `CategoryTheory.comp`.
 
 This file is kept separate from `Mathlib/Algebra/Ring/Equiv.lean` so that
-`Mathlib/GroupTheory/Perm.lean` is free to use equivalences (and other files that use them) before
+`Mathlib/Data/Fintype/Perm.lean` is free to use equivalences (and other files that use them) before
 the group structure is defined.
 
 ## Tags