fix(lean): remove company-lean

company-lean was removed from MELPA. Since lean4 support is around the
corner and Doom has deprecated its support for Company, I'll simply
remove this package.

Ref: melpa/melpa@11196af312
Fix: #8159

modules/lang/lean/README.org

@@ -14,7 +14,6 @@ This module adds support for the [[https://leanprover.github.io/about/][Lean pro
 
 ** Packages
 - [[doom-package:lean-mode]]
-- [[doom-package:company-lean]] if [[doom-module::completion company]]
 
 ** TODO Hacks
 #+begin_quote

modules/lang/lean/config.el

@@ -26,11 +26,3 @@
         "h" #'lean-hole
         "m" #'lean-message-boxes-toggle
         "e" #'lean-execute))
-
-
-(use-package! company-lean
-  :when (modulep! :completion company)
-  :after lean-mode
-  :init
-  (advice-add #'company-lean-hook :override #'ignore)
-  (set-company-backend! 'lean-mode 'company-lean))

modules/lang/lean/packages.el

@@ -2,6 +2,3 @@
 ;;; lang/lean/packages.el
 
 (package! lean-mode :pin "99d6a34dc5b12f6e996e9217fa9f6fe4a6af037a")
-
-(when (modulep! :completion company)
-  (package! company-lean :pin "99d6a34dc5b12f6e996e9217fa9f6fe4a6af037a"))