chore: remove unused member from TagSet (#22930)

Co-authored-by: Tristan Su <suqing.sq@alibaba-inc.com>

influxql/query/result.go

@@ -17,7 +17,6 @@ const (
 // TagSet is a fundamental concept within the query system. It represents a composite series,
 // composed of multiple individual series that share a set of tag attributes.
 type TagSet struct {
-	Tags       map[string]string
 	Filters    []influxql.Expr
 	SeriesKeys []string
 	Key        []byte

tsdb/index.go

@@ -3122,7 +3122,6 @@ func (is IndexSet) TagSets(sfile *SeriesFile, name []byte, opt query.IteratorOpt
 		if !ok {
 			// This TagSet is new, create a new entry for it.
 			tagSet = &query.TagSet{
-				Tags: nil,
 				Key: tagsAsKey,
 			}
 		}