[skip e2e]Add comment for getDimension in indexcoord (#13761)

Signed-off-by: Cai.Zhang <cai.zhang@zilliz.com>

internal/indexcoord/util.go

@@ -25,6 +25,7 @@ import (
 	"github.com/milvus-io/milvus/internal/proto/schemapb"
 )
 
+// getDimension gets the dimension of data from building index request.
 func getDimension(req *indexpb.BuildIndexRequest) (int64, error) {
 	for _, kvPair := range req.GetTypeParams() {
 		key, value := kvPair.GetKey(), kvPair.GetValue()