Use a scoped mypy type ignore

JSONSettings override dict but the signature of get is different.

Just silence that type of warning while getting type check for the type of the
arguments.

lms/models/json_settings.py

@@ -72,7 +72,7 @@ class JSONSettings(MutableDict):
     An optional spec for the acceptable fields and types.
     """
 
-    def get(self, group, key, default=None):  # type: ignore
+    def get(self, group: str, key: str, default=None):  # type: ignore[override]
         """
         Return the requested setting or None.
 

lms/resources/_js_config/__init__.py

@@ -7,7 +7,7 @@
 from lms.error_code import ErrorCode
 from lms.events import LTIEvent
 from lms.js_config_types import DashboardConfig, DashboardRoutes, User
-from lms.models import Assignment, Course, Grouping
+from lms.models import ApplicationInstance, Assignment, Course, Grouping
 from lms.product.blackboard import Blackboard
 from lms.product.canvas import Canvas
 from lms.product.d2l import D2L
@@ -48,7 +48,7 @@ def _h_user(self):
         return self._lti_user.h_user
 
     @property
-    def _application_instance(self):
+    def _application_instance(self) -> ApplicationInstance:
         return self._lti_user.application_instance
 
     def add_document_url(  # pylint: disable=too-complex,too-many-branches,useless-suppression  # noqa: PLR0912