Update filter_spans.py (Azure#38774)

Author: lzchen

sdk/monitor/azure-monitor-opentelemetry/samples/tracing/filter_spans.py

@@ -14,7 +14,7 @@
 class SpanFilteringProcessor(SpanProcessor):
 
     # Prevents exporting spans that are of kind INTERNAL
-    def on_start(self, span, parent_context):
+    def on_start(self, span, parent_context):  # type: ignore
         # Check if the span is an internal activity.
         if span._kind is SpanKind.INTERNAL:
             # Create a new span context with the following properties: