shelly wifi levels adapted

check_shelly

@@ -9,7 +9,7 @@ import urllib.request
 CHECKS = ['wifi', 'mqtt', 'memory', 'filesystem', 'temperature']
 #
 WIFI_QUALITY_ERROR = -92
-WIFI_QUALITY_WARNING = -88
+WIFI_QUALITY_WARNING = -90
 #
 RAM_ERROR = .15
 RAM_WARNING = .30