Make file_cache logging less verbose (neondatabase#4601)

## Problem


Message "set local file cache limit to..." polutes compute logs.

## Summary of changes

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

Co-authored-by: Konstantin Knizhnik <[email protected]>

pgxn/neon/file_cache.c

@@ -190,7 +190,7 @@ lfc_change_limit_hook(int newval, void *extra)
 		hash_search(lfc_hash, &victim->key, HASH_REMOVE, NULL);
 		lfc_ctl->used -= 1;
 	}
-	elog(LOG, "set local file cache limit to %d", new_size);
+	elog(DEBUG1, "set local file cache limit to %d", new_size);
 	LWLockRelease(lfc_lock);
 }