docs: add Filter data to ToC under data flows section

Author: jlian

articles/iot-operations/toc.yml

@@ -212,6 +212,9 @@ items:
               - name: Enrich data
                 href: connect-to-cloud/concept-dataflow-enrich.md
                 displayName: data flow, transform, context, contextualization
+              - name: Filter data
+                href: connect-to-cloud/howto-dataflow-filter.md
+                displayName: data flow, filter, drop, condition, boolean, expression
               - name: Schemas
                 href: connect-to-cloud/concept-schema-registry.md
                 displayName: data flow, serialize, deserialize, schema registry