🌐(frontend) enhance few English traductions

Found few issues, fixed them.

src/frontend/src/locales/en/notifications.json

@@ -1,10 +1,10 @@
 {
   "defaultName": "A contributor",
   "joined": {
-    "description": "{{name}} join the room"
+    "description": "{{name}} has joined the room"
   },
   "raised": {
-    "description": "{{name}} raised its hand.",
+    "description": "{{name}} has raised their hand.",
     "cta": "Open waiting list"
   }
 }

src/frontend/src/locales/en/rooms.json

@@ -65,7 +65,7 @@
     "muteYourself": "Close your mic",
     "muteParticipant": "Close the mic of {{name}}",
     "muteParticipantAlert": {
-      "description": "Mute {{name}} for all participants? {{name}} is the only person who can unmute themselves.",
+      "description": "Mute {{name}} for all participants? {{name}} will be the only one who can unmute themselves.",
       "confirm": "Mute",
       "cancel": "Cancel"
     },