fix documented introduction of the auto C driver download

It is introduced in 3.9.0 as part of CXX-2695.

Author: kevinAlbs

docs/content/mongocxx-v3/installation/advanced.md

@@ -23,7 +23,7 @@ The above command would produce libraries named `libcustom_bsoncxx.so` and `libc
 
 The mongocxx driver builds on top of the [MongoDB C driver](https://www.mongodb.com/docs/drivers/c/).
 
-The build of mongocxx-3.8.1 automatically downloads and installs the C driver if the C driver is not detected.
+The build of mongocxx-3.9.0 automatically downloads and installs the C driver if the C driver is not detected.
 To use an existing install of the C driver, set `CMAKE_PREFIX_PATH` to the directory containing the C driver install.
 
 * For mongocxx-3.8.x, libmongoc 1.24.0 or later is required.