SA14/CI: Suppress alert from lgtm.com

lgtm.com issued an alert like::

Module 'sqlalchemy' is imported with both 'import' and 'import from'

See: https://lgtm.com/projects/g/crate/crate-python/rev/pr-8ea3b257a334a41cdb531d681072752e662eee56.

The corresponding rule in lgtm.yml introduced by bcf9fff does not seem
to work.

src/crate/client/sqlalchemy/compiler.py

@@ -22,8 +22,8 @@
 import string
 from collections import defaultdict
 
-import sqlalchemy as sa
-from sqlalchemy.sql import compiler, crud, selectable
+import sqlalchemy as sa  # lgtm[py/import-and-import-from]
+from sqlalchemy.sql import compiler, crud, selectable  # lgtm[py/import-and-import-from]
 from .types import MutableDict
 from .sa_version import SA_VERSION, SA_1_4