Remove unnecessary sqlite3 Timestamp import from summaries.py and indicators.py to fix mypy errors (#938)

Author: justinpolygon

polygon/rest/models/indicators.py

@@ -1,4 +1,3 @@
-from sqlite3 import Timestamp
 from typing import Optional, Any, Dict, List, Union
 from ...modelclass import modelclass
 from .aggs import Agg

polygon/rest/models/summaries.py

@@ -1,4 +1,3 @@
-from sqlite3 import Timestamp
 from typing import Optional
 from ...modelclass import modelclass
 from .tickers import Branding