Revert "add tests for new lowmem option"
Revert "add tests for new lowmem option"

(lowmem tests should not duplicate existing tests but directly
compare lowmem vs no-lowmem)
This reverts commit cd56ef2ce661d2a671f28b0889d96e82550d098d.

sidward/bart,mrirecon/bart,sdimoudi/bart,sdimoudi/bart,sidward/bart,sidward/bart,sidward/bart,mrirecon/bart,sidward/bart,mrirecon/bart,sdimoudi/bart,mrirecon/bart,sdimoudi/bart,mrirecon/bart,sdimoudi/bart