Reduce the log severity of profiling agent discovery

Example:

[https://github.com/apache/beam/blob/b953645ed6db837d24284d7fe1fe091e7309f821/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/profiler/ScopedProfiler.java#L138](https://github.com/apache/beam/blob/b953645ed6db837d24284d7fe1fe091e7309f821/runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/profiler/ScopedProfiler.java#L138)

These should not be at warning severity, even if the profiling agent is not present since it's in most cases users do not run their jobs with profiling.

Imported from Jira [BEAM-7020](https://issues.apache.org/jira/browse/BEAM-7020). Original Jira may contain additional context.
Reported by: davidyan.