filter.py: don't recurse when staging dependencies
Description
Don't recurse when staging the dependencies of the filter element. Also bump the element's version so cached artifacts would be invalidated.
Fixes #883 (closed)
The fix was kindly suggested by @juergbi.
CHANGELOG/Release Notes
The filter element no longer stages and filters its indirect dependencies.
CC: @jonathanmaw
CC: @jennis
Edited by Dor Askayo