chore: Edit intl entry instead of adding new one

lib/l10n/intl_en.arb

@@ -2450,7 +2450,7 @@
   },
   "pinMessage": "Pin to room",
   "@pinMessage": {},
-  "confirmEventUnpin": "Are you sure to permanently unpin the event?",
+  "confirmEventUnpin": "Are you sure you want to unpin this message?",
   "@confirmEventUnpin": {},
   "emojis": "Emojis",
   "@emojis": {},
@@ -3374,7 +3374,5 @@
   "moreEvents": "More events",
   "@moreEvents": {},
   "declineInvitation": "Decline invitation",
-  "@declineInvitation": {},
-  "confirmMessageUnpin": "Are you sure you want to unpin this message?",
-  "@confirmMessageUnpin": {}
+  "@declineInvitation": {}
 }

lib/pages/chat/chat.dart

@@ -1177,7 +1177,7 @@ class ChatController extends State<ChatPageWithRoom>
     final response = await showOkCancelAlertDialog(
       context: context,
       title: L10n.of(context).unpin,
-      message: L10n.of(context).confirmMessageUnpin,
+      message: L10n.of(context).confirmEventUnpin,
       okLabel: L10n.of(context).unpin,
       cancelLabel: L10n.of(context).cancel,
     );