Plex api update (#11423)

* Updated plexapi to 3.0.5

* Removed removed server obj that was being used for the media URL generation as .url() is available in self._session
seasons() no longer exists -> renamed to season()
season() returns obj not list so corrected
season.index returns int, cast to str to zerofill

* Fixed Linting

homeassistant/components/sensor/plex.py

@@ -16,7 +16,7 @@ from homeassistant.helpers.entity import Entity
 from homeassistant.util import Throttle
 import homeassistant.helpers.config_validation as cv
 
-REQUIREMENTS = ['plexapi==3.0.3']
+REQUIREMENTS = ['plexapi==3.0.5']
 
 _LOGGER = logging.getLogger(__name__)