tests/mutation_reader_test: combined_mutation_reader_test: use SEASTAR_THREAD_TEST_CASE
tests/mutation_reader_test: combined_mutation_reader_test: use SEASTAR_THREAD_TEST_CASE

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