support/download: cleanup svn backend

support/download: cleanup svn backend

Commit 89f5e9893 (support/download/svn: generate reproducible svn
archives) did what it said, but can be siplified a bit.

Indeed, we are doing an svn export, so we won't have any of the .svn
directories, neither at the root of the extract, nor in any of the
sub-directories.

As such, we do not need to filter them out  when we generate the list
of files to include in the archive.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Heiko Thiery <heiko.thiery@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Vincent Fazio <vfazio@xes-inc.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: Vincent Fazio <vfazio@xes-inc.com>