[Core] Fix circular import (Azure#38776)

An import used for typing is now guarded behing the TYPE_CHECKING flag
from the typing module.

Signed-off-by: Paul Van Eck <paulvaneck@microsoft.com>

sdk/core/azure-core/azure/core/settings.py

@@ -43,10 +43,13 @@
     Generic,
     Mapping,
     List,
+    TYPE_CHECKING,
 )
-from azure.core.tracing import AbstractSpan
 from ._azure_clouds import AzureClouds
 
+if TYPE_CHECKING:
+    from azure.core.tracing import AbstractSpan
+
 ValidInputType = TypeVar("ValidInputType")
 ValueType = TypeVar("ValueType")