Add GDPR classification tag for new event (#21135)

Author: luabud

src/client/telemetry/pylance.ts

@@ -137,6 +137,11 @@
       "name" : { "classification": "SystemMetaData", "purpose": "FeatureInsight" }
    }
 */
+/* __GDPR__
+   "language_server/goto_def_inside_string" : {
+      "resultlength" : { "classification": "SystemMetaData", "purpose": "FeatureInsight" }
+   }
+*/
 /* __GDPR__
    "language_server/import_heuristic" : {
       "avgcost" : { "classification": "SystemMetaData", "purpose": "FeatureInsight" },