action_sheet [nfc]: Make showMessageActionSheet's context an unnamed param

Signed-off-by: Zixuan James Li <zixuan@zulip.com>

Author: PIG208

lib/widgets/action_sheet.dart

@@ -146,7 +146,7 @@ class ActionSheetCancelButton extends StatelessWidget {
 /// Show a sheet of actions you can take on a message in the message list.
 ///
 /// Must have a [MessageListPage] ancestor.
-void showMessageActionSheet({required BuildContext context, required Message message}) {
+void showMessageActionSheet(BuildContext context, {required Message message}) {
   final store = PerAccountStoreWidget.of(context);
 
   // The UI that's conditioned on this won't live-update during this appearance

lib/widgets/message_list.dart

@@ -1273,7 +1273,7 @@ class MessageWithPossibleSender extends StatelessWidget {
 
     return GestureDetector(
       behavior: HitTestBehavior.translucent,
-      onLongPress: () => showMessageActionSheet(context: context, message: message),
+      onLongPress: () => showMessageActionSheet(context, message: message),
       child: Padding(
         padding: const EdgeInsets.symmetric(vertical: 4),
         child: Column(children: [