tests/*cqlengine/management: fix parameters passed to compaction

at some point scylla started validation of the arguments to compaction
and newer versions rejects the values passed from this test

chnaged it to something within the values expected

Author: fruch

tests/integration/cqlengine/management/test_compaction_settings.py

@@ -60,7 +60,7 @@ class SizeTieredCompactionChangesDetectionTest(Model):
 
             __options__ = {'compaction': {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy',
                                           'bucket_high': '20',
-                                          'bucket_low': '10',
+                                          'bucket_low': '0.5',
                                           'max_threshold': '200',
                                           'min_threshold': '100',
                                           'min_sstable_size': '1000',