bug#65655: 30.0.50; Minor oversights in integer->natnum :type change

[Mauro Aranda]

The type of the following two options was changed from integer to natnum:
blink-cursor-blinks and url-max-redirections
as part of this commit:

commit 9d866a1f8da870dcf82f87d5ed9d5ca932d5477b
Author: Stefan Kangas <stefankangas@gmail.com>
Date:   Tue Jul 5 16:26:45 2022 +0200

    Make some defcustom types more restrictive


But the docstring of blink-cursor-blinks says:
"Use 0 or negative value to blink forever."
Now a negative value can't be used, so it would be good to adapt the
docstring, at least.

And the docstring of url-max-redirections says:
"A negative number means to honor an unlimited number of redirection
requests."
I suggest to change its type back to integer.