Revert "Remove suggestion for using LEAVE phasers"

This reverts commit d1f2d49.

Not only this .close is not related to the thing experienced in the
ticket, but it also talks about exceptions in other parts of your code
(not even related to the file you want to close).

Author: AlexDaniel

doc/Type/IO.pod6

@@ -229,7 +229,8 @@ written equivalently like so:
     close $fh;
 
 When a file was opened for writing, closing it is important to ensure that all
-contents are actually written to the file.
+contents are actually written to the file. You may want to consider using a
+L<LEAVE|/language/phasers#LEAVE> phaser to guard against exceptions.
 
 =head2 sub slurp