Fix: add missing license header (#6073)

Author: fgksgf

pkg/utils/integer_test.go

@@ -1,7 +1,17 @@
 // Copyright 2024 PingCAP, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with t
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 package utils
 
 import (