purescript-indentation.el: rm defvar for delete-active-region

All supported Emacs versions have the variable, so no need to have it
defined still.

Author: Hi-Angel

purescript-indentation.el

@@ -34,10 +34,9 @@
 
 (require 'syntax)
 (require 'cl-lib)
+(require 'simple)
 (require 'purescript-vars)
 
-(defvar delete-active-region)
-
 ;; Dynamically scoped variables.
 (defvar following-token)
 (defvar current-token)