Bug 29015: (QA follow-up) Change collection code to be just collection

Bug 29015: (QA follow-up) Change collection code to be just collection

We did some clean-up in that area a little while ago, agreeing that
as we acutally display the descriptions, the label should be just
"collection".

This patch also removes some ():

Before:
4 items found for Centerville and item type:(Books) and collection: (Reference) and shelving location: (General Stacks)

Now:
4 items found for Centerville and item type: Books and collection: Reference and shelving location: General Stacks

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>