opt ui of Windows session dialog (#13303)

Signed-off-by: 21pages <sunboeasy@gmail.com>

flutter/lib/common/widgets/dialog.dart

@@ -2121,8 +2121,10 @@ void showWindowsSessionsDialog(
 
     return CustomAlertDialog(
       title: null,
-      content: msgboxContent(type, title, text),
-      actions: [
+      content: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          msgboxContent(type, title, text).marginOnly(bottom: 12),
           ComboBox(
               keys: sids,
               values: names,
@@ -2130,6 +2132,9 @@ void showWindowsSessionsDialog(
               onChanged: (value) {
                 selectedUserValue = value;
               }),
+        ],
+      ),
+      actions: [
         dialogButton('Connect', onPressed: submit, isOutline: false),
       ],
     );