Fix new linter error when importing annotationlib (#3143)

(cherry picked from commit 026f515)

Author: miguelgrinberg

elasticsearch/dsl/document_base.py

@@ -39,7 +39,7 @@
 try:
     import annotationlib
 except ImportError:
-    annotationlib = None
+    annotationlib = None  # type: ignore[assignment]
 
 try:
     from types import UnionType