Remove newline from exception messages.
Remove newline from exception messages.

They are inconsistent with other uses of malformed_sstable_exception
and incompatible with adding " in sstable ..." to the message.

Signed-off-by: Rafael Ávila de Espíndola <1975039f9046bf513b77c0c5639a0efc25f00e7f@scylladb.com>

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