fix: label typo (#755)

The use of the term connection in the singular form is correct because in the phrase "connection history" it acts as a noun adjunct, which is generally used in the singular form with a few specific exceptions.

Author: filippocarletti

src/i18n/en.json

@@ -1994,7 +1994,7 @@
       "user_not_valid": "Invalid user: the user has a VPN configuration but it's not present inside the remote user database.",
       "tabs": {
         "road_warrior_server": "Road Warrior server",
-        "connections_history": "Connections history"
+        "connections_history": "Connection history"
       },
       "history": {
         "account": "Account",