link fix (#222)

Author: kyuan-mongodb

source/fundamentals/monitoring.txt

@@ -418,7 +418,8 @@ tracing system other than Zipkin, you must write a command event listener that
 manages `spans <https://docs.spring.io/spring-cloud-sleuth/docs/current-SNAPSHOT/reference/html/getting-started.html#getting-started-terminology>`__
 for your desired distributed tracing system. To see an implementation of such a
 listener, see the
-:github:`TraceMongoCommandListener <spring-cloud/spring-cloud-sleuth/blob/main/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/mongodb/TraceMongoCommandListener.java>`
+:github:`TraceMongoCommandListener
+<spring-cloud/spring-cloud-sleuth/blob/eb01d5952b2e736970efbe3fc7e9784d119eeae9/spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/mongodb/TraceMongoCommandListener.java>`
 class in the Spring Cloud Sleuth source code.
 
 To learn more about Spring Cloud Sleuth, see