Change edge worker heartbeat message from info to debug

[KidAmnesiac1]

Change log level from info to debug for Edge worker status requests

The "Request to get status of Edge Worker received." message in
signal_status() drops from info to debug.

Why: this line fires whenever someone runs airflow edge status. That
command just asks the worker what it's doing and prints the answer — it
doesn't change anything about the worker. It's also the sort of command
people put in a loop: health checks, monitoring scripts, or an operator
keeping an eye on a worker that's draining. Every one of those calls
leaves an info line in the log saying someone asked a question.

The other half of the same if-statement makes the point. When a
maintenance marker is present the worker really does change state, and
that branch logs at info — which is right. Answering a status query
isn't a change, so it shouldn't sit at the same level.

The command sending the signal already logs at debug on its side
("Sending SIGUSR2 to worker pid ..."), so this just gets both ends to
agree.

No behaviour change. The status file is written exactly as before and
airflow edge status prints the same thing. If you want these messages
back, set the edge worker log level to DEBUG.

---

Was generative AI tooling used to co-author this PR?

• No

---

• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst, in airflow-core/newsfragments. You can add this file in a follow-up commit after the PR is created so you know the PR number.