Change Unifi Widget "System Uptime" to "Uptime" (#2389)

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Co-authored-by: shamoon <4887959+shamoon@users.noreply.github.com>

public/locales/en/common.json

@@ -48,7 +48,7 @@
     },
     "unifi": {
         "users": "Users",
-        "uptime": "System Uptime",
+        "uptime": "Uptime",
         "days": "Days",
         "wan": "WAN",
         "lan": "LAN",