Refactor session close as xorm already does everything needed internally (#2020)

models/repo_editor.go

@@ -401,7 +401,7 @@ func DeleteUploads(uploads ...*Upload) (err error) {
 	}
 
 	sess := x.NewSession()
-	defer sessionRelease(sess)
+	defer sess.Close()
 	if err = sess.Begin(); err != nil {
 		return err
 	}