flat_mutation_reader: fix indentation in consume_pausable
flat_mutation_reader: fix indentation in consume_pausable

Code was left with wrong indentation by the previous commit that
removed do_with call around the code that's currently present.

Signed-off-by: Piotr Jastrzebski <2c0eb4a25a7cde333ff2d0860cb06051925fd74f@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla