CDRIVER-6138 replace broken link (#2172)

Use soon-to-be-published new link added in DOCSP-54877.

Author: kevinAlbs

src/libmongoc/doc/conf.py

@@ -205,7 +205,7 @@ def _maybe_update_inventories(app: Sphinx):
 
 .. _configuring_tls: https://www.mongodb.com/docs/languages/c/c-driver/current/libmongoc/guides/configuring_tls/
 
-.. _connection-pooling: https://www.mongodb.com/docs/languages/c/c-driver/current/libmongoc/guides/connection-pooling/
+.. _connection-pooling: https://www.mongodb.com/docs/languages/c/c-driver/current/connect/connection-pools/.
 
 .. _in-use-encryption: https://www.mongodb.com/docs/languages/c/c-driver/current/libmongoc/guides/in-use-encryption/