fix: Avoid solidity line length hightlighting being applied globally

lisp/init-solidity.el

 ;; https://gitlab.haskell.org/ghc/ghc/wikis/emacs
 (require 'whitespace)
 (defun solidity-custom-line-length ()
-  (setq whitespace-style '(face lines-tail))
-  (setq whitespace-line-column 145)
-  (global-whitespace-mode t))
+  (setq-local whitespace-style '(face lines-tail))
+  (setq-local whitespace-line-column 145)
+  (whitespace-mode 1))
 
 (add-hook 'solidity-mode-hook 'solidity-custom-line-length)