chore: clean up unused imports in db migration scripts (apache#19630)

superset/migrations/versions/07071313dd52_change_fetch_values_predicate_to_text.py

@@ -30,9 +30,7 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy import and_, func, or_
-from sqlalchemy.dialects import postgresql
-from sqlalchemy.sql.schema import Table
+from sqlalchemy import func
 
 from superset import db
 from superset.connectors.sqla.models import SqlaTable

superset/migrations/versions/181091c0ef16_add_extra_column_to_columns_model.py

@@ -28,9 +28,6 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import postgresql
-
-from superset.utils.core import generic_find_constraint_name
 
 
 def upgrade():

superset/migrations/versions/19e978e1b9c3_add_report_format_to_report_schedule_.py

@@ -28,7 +28,6 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import postgresql
 
 
 def upgrade():

superset/migrations/versions/3ba29ecbaac5_change_datatype_of_type_in_basecolumn.py

@@ -28,7 +28,6 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import postgresql
 
 
 def upgrade():

superset/migrations/versions/6d20ba9ecb33_add_last_saved_at_to_slice_model.py

@@ -28,7 +28,6 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import postgresql
 
 
 def upgrade():

superset/migrations/versions/73fd22e742ab_add_dynamic_plugins_py.py

@@ -28,7 +28,6 @@
 
 import sqlalchemy as sa
 from alembic import op
-from sqlalchemy.dialects import postgresql
 
 
 def upgrade():