chore: bump Std4 (#6695)

The file [`Mathlib.Util.Pickle`](leanprover-community/batteries#211) has been upstreamed to std4, as has the declaration [`String.count`](leanprover-community/batteries#220).



Co-authored-by: Scott Morrison <scott.morrison@gmail.com>

Mathlib.lean

@@ -3420,7 +3420,6 @@ import Mathlib.Util.IncludeStr
 import Mathlib.Util.LongNames
 import Mathlib.Util.MemoFix
 import Mathlib.Util.PiNotation
-import Mathlib.Util.Pickle
 import Mathlib.Util.Qq
 import Mathlib.Util.SleepHeartbeats
 import Mathlib.Util.Superscript

Mathlib/Data/String/Defs.lean

@@ -45,10 +45,6 @@ def mapTokens (c : Char) (f : String → String) : String → String :=
   intercalate (singleton c) ∘ List.map f ∘ (·.split (· = c))
 #align string.map_tokens String.mapTokens
 
-/-- Count the occurrences of a character in a string. -/
-def count (s : String) (c : Char) : Nat :=
-  s.foldl (fun n d => if d = c then n + 1 else n) 0
-
 /-- `getRest s t` returns `some r` if `s = t ++ r`.
 If `t` is not a prefix of `s`, it returns `none`. -/
 def getRest (s t : String) : Option String :=

Mathlib/Tactic/LibrarySearch.lean

@@ -3,7 +3,7 @@ Copyright (c) 2021 Gabriel Ebner. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Gabriel Ebner, Scott Morrison
 -/
-import Mathlib.Util.Pickle
+import Std.Util.Pickle
 import Mathlib.Tactic.Cache
 import Mathlib.Tactic.SolveByElim
 import Mathlib.Data.MLList.Heartbeats

Mathlib/Tactic/Rewrites.lean

@@ -3,7 +3,7 @@ Copyright (c) 2023 Scott Morrison. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Scott Morrison
 -/
-import Mathlib.Util.Pickle
+import Std.Util.Pickle
 import Mathlib.Data.MLList.Heartbeats
 import Mathlib.Lean.Meta.DiscrTree
 import Mathlib.Tactic.Cache

lake-manifest.json

@@ -36,7 +36,7 @@
   {"git":
    {"url": "https://github.com/leanprover/std4",
     "subDir?": null,
-    "rev": "49353fa54abdac7221fe27f7b57a6ed9ff559d5c",
+    "rev": "61a6507eff4dd71c01e0c7e194bc569d4719a6d3",
     "opts": {},
     "name": "std",
     "inputRev?": "main",