Update English (United States) translation

locales/en-US.json

@@ -71,7 +71,7 @@
     "Preferred video quality: ": "Preferred video quality: ",
     "Player volume: ": "Player volume: ",
     "Default comments: ": "Default comments: ",
-    "youtube": "youtube",
+    "youtube": "YouTube",
     "reddit": "reddit",
     "Default captions: ": "Default captions: ",
     "Fallback captions: ": "Fallback captions: ",