[Test] Don't allow empty block in docker integration tests

[frisitano]

We should probably remove this line for the Docker tests:

rollup-node/tests/launch_rollup_node_sequencer.bash

Line 21 in 07c1668

--sequencer.allow-empty-blocks \

If we don't allow empty blocks in the Docker tests then we would've caught the error already during testing.

Originally posted by @jonastheis in #391 (review)