fix: adresse the check() linter warning

check warning: The instance argument in the `check()` function is
going to be deprecated in Agent 6. Please use `self.instance` instead.

kube_apiserver_metrics/datadog_checks/kube_apiserver_metrics/kube_apiserver_metrics.py

@@ -95,7 +95,7 @@ def __init__(self, name, init_config, instances=None):
 
     def check(self, instance):
         if self.kube_apiserver_config is None:
-            self.kube_apiserver_config = self.get_scraper_config(instance)
+            self.kube_apiserver_config = self.get_scraper_config(self.instance)
 
         if not self.kube_apiserver_config['metrics_mapper']:
             url = self.kube_apiserver_config['prometheus_url']