Update comment about parsing id types

ui/src/trace_processor/perfetto_sql_type.ts

diff --git a/ui/src/trace_processor/perfetto_sql_type.ts b/ui/src/trace_processor/perfetto_sql_type.ts
index f3ac79a..96891de 100644
--- a/ui/src/trace_processor/perfetto_sql_type.ts
+++ b/ui/src/trace_processor/perfetto_sql_type.ts
@@ -129,6 +129,7 @@
     });
   }
   if (value === 'id') {
+    // The plain `ID` are resolved into `ID($current_table.$current_column)`.
     return okResult({
       kind: 'id',
       source: {