[skip ci] Add comment for CheckCtxValid (#13202)

Signed-off-by: shaoyue.chen <shaoyue.chen@zilliz.com>

internal/util/funcutil/func.go

@@ -185,6 +185,7 @@ func GetAttrByKeyFromRepeatedKV(key string, kvs []*commonpb.KeyValuePair) (strin
 	return "", errors.New("key " + key + " not found")
 }
 
+// CheckCtxValid check if the context is valid
 func CheckCtxValid(ctx context.Context) bool {
 	return ctx.Err() != context.DeadlineExceeded && ctx.Err() != context.Canceled
 }