Update cpp-use-cases.md

fix a bug in the doc, the target 'hello-greet' should be in package 'main', not in 'lib'

Closes #7745.

PiperOrigin-RevId: 240433186
diff --git a/site/docs/cpp-use-cases.md b/site/docs/cpp-use-cases.md
index 4844902..47c6353 100644
--- a/site/docs/cpp-use-cases.md
+++ b/site/docs/cpp-use-cases.md
@@ -217,13 +217,13 @@
     copts = ["-Iexternal/gtest/include"],
     deps = [
         "@gtest//:main",
-        "//lib:hello-greet",
+        "//main:hello-greet",
     ],
 )
 ```
 
 Note that in order to make `hello-greet` visible to `hello-test`, we have to add
-`"//test:__pkg__",` to the `visibility` attribute in `./lib/BUILD`.
+`"//test:__pkg__",` to the `visibility` attribute in `./main/BUILD`.
 
 Now you can use `bazel test` to run the test.