Fix documentation for ENABLE_LEARNER_RECORDS

Commit 3222d3fd (LEARNER-5987)
introduced the ENABLE_LEARNER_RECORDS site configuration flag, but
incorrectly referred to it as ENABLE_CREDENTIALS_RECORDS in the
documentation for the credentials service.

Fix the reference with the correct flag name.

openedx/core/djangoapps/credentials/docs/site_config.rst

@@ -3,8 +3,8 @@ Site Configuration
 
 These are the site configuration flags that affect Credentials features.
 
-ENABLE_CREDENTIALS_RECORDS
---------------------------
+ENABLE_LEARNER_RECORDS
+----------------------
 
 Controls whether the LMS integrates with the Learner Records feature in Credentials. Specifically, this turns on some web buttons that link to a learner's record on the Credentials IDA and enables some data being passed to Credentials related to those records.