chore(spans): Remove spansIndexed from events (#95481)

- This removes the option to pass dataset=spansIndexed to the events
endpoints and query the deprecated indexed spans dataset

Author: wmak

src/sentry/snuba/utils.py

@@ -11,7 +11,6 @@
     metrics_performance,
     ourlogs,
     profiles,
-    spans_indexed,
     spans_metrics,
     spans_rpc,
     transactions,
@@ -34,7 +33,6 @@
     "issuePlatform": issue_platform,
     "profileFunctions": functions,
     "spans": spans_rpc,
-    "spansIndexed": spans_indexed,
     "spansMetrics": spans_metrics,
     "transactions": transactions,
 }