cindex: drop redundant close on regular FH

cindex: drop redundant close on regular FH

There's no need to waste optree space on close() statements for
file handles which are (effectively) read-only on their last use
and incapable of error checking in our Perl code (since they're
only read by git).

Let Perl refcounting take care of it so we have less code to
wade through when focusing on `close' statements which actually
matter.