Googletest export

add missing using ::testing::DoAll when DoAll used in example

PiperOrigin-RevId: 402416497
diff --git a/docs/gmock_cook_book.md b/docs/gmock_cook_book.md
index f7954a2..b41c5b9 100644
--- a/docs/gmock_cook_book.md
+++ b/docs/gmock_cook_book.md
@@ -1980,6 +1980,7 @@
 
 ```cpp
 using ::testing::_;
+using ::testing::DoAll;
 using ::testing::Return;
 using ::testing::SetArgPointee;