test.py: Increase memory for row_cache_stress_test
test.py: Increase memory for row_cache_stress_test

Cells and rows will require more memory when we start caching the cell
hash.

Signed-off-by: Duarte Nunes <a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>

scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla