druid connector: avoid using 'dimensions' for scan queries

After the following PyDruid change (contained in version 0.5.2)
the Superset Histogram charts rendered with Druid data are
broken:

druid-io/pydruid@0a59a70

Bump the pydruid requirements accordingly in setup.py

Issue: apache#7368

setup.py

@@ -92,7 +92,7 @@ def get_git_sha():
         'parsedatetime',
         'pathlib2',
         'polyline',
-        'pydruid>=0.4.3',
+        'pydruid>=0.5.2',
         'python-dateutil',
         'python-geohash',
         'pyyaml>=3.13',

superset/connectors/druid/models.py

@@ -1118,7 +1118,8 @@ def run_query(  # noqa / druid
             columns.append('__time')
             del qry['post_aggregations']
             del qry['aggregations']
-            qry['dimensions'] = columns
+            del qry['dimensions']
+            qry['columns'] = columns
             qry['metrics'] = []
             qry['granularity'] = 'all'
             qry['limit'] = row_limit