Rewrite the Push Notifications section in the configuration template (#4805)

- also update the European Union related information for a working setup
- fixes https://github.com/dani-garcia/vaultwarden/issues/4609

.env.template

@@ -92,15 +92,20 @@
 ##########################
 
 ## Enables push notifications (requires key and id from https://bitwarden.com/host)
-## If you choose "European Union" Data Region, uncomment PUSH_RELAY_URI and PUSH_IDENTITY_URI then replace .com by .eu
 ## Details about mobile client push notification:
 ## - https://github.com/dani-garcia/vaultwarden/wiki/Enabling-Mobile-Client-push-notification
 # PUSH_ENABLED=false
 # PUSH_INSTALLATION_ID=CHANGEME
 # PUSH_INSTALLATION_KEY=CHANGEME
-## Don't change this unless you know what you're doing.
+
+# WARNING: Do not modify the following settings unless you fully understand their implications!
+# Default Push Relay and Identity URIs
 # PUSH_RELAY_URI=https://push.bitwarden.com
 # PUSH_IDENTITY_URI=https://identity.bitwarden.com
+# European Union Data Region Settings
+# If you have selected "European Union" as your data region, use the following URIs instead.
+# PUSH_RELAY_URI=https://api.bitwarden.eu
+# PUSH_IDENTITY_URI=https://identity.bitwarden.eu
 
 #####################
 ### Schedule jobs ###