Remove non-errors from logs

[mbroecheler]

Flink's Web UI / REST endpoint will log errors when it cannot find a job for a request, like:

2025-11-03 14:28:36.244 [flink-rest-server-netty-worker-thread-1] ERROR org.apache.flink.runtime.rest.handler.job.checkpoints.CheckpointingStatisticsHandler - Exception occurred in REST handler: Job 7537d1346397f930741fbffeadfe448e not found

This is usually a user error but it looks like something is wrong with checkpointing.
Let's remove this from the logs so it doesn't print these log statements.
Generalize to any "Job XYZ not found" log statements from the rest handler.