Set httpx and httpcore logger level to WARNING (#176)

`httpx` and `httpcore` (used by `lightkube`) have noisy INFO & DEBUG
level logs

Supersedes #145. It still seems a bit backwards to me to enable DEBUG
level logs for all python dependencies and then manually disable logging
for dependencies of our dependencies. Personally, I only think DEBUG
level logs are useful for charm ecosystem code (e.g. ops, the charm,
charm libs)—but it seems like the consensus [from this
discussion](#145 (comment))
is different

Author: carlcsaposs-canonical

src/kubernetes_charm.py

@@ -25,6 +25,8 @@
 import upgrade
 
 logger = logging.getLogger(__name__)
+logging.getLogger("httpx").setLevel(logging.WARNING)
+logging.getLogger("httpcore").setLevel(logging.WARNING)
 
 
 class KubernetesRouterCharm(abstract_charm.MySQLRouterCharm):