fix: All license dialogs should look the same

lib/src/ui/pages/about.dart

@@ -64,12 +64,17 @@ class AboutPage extends StatelessWidget {
                             await showDialog<void>(
                               context: context,
                               builder: (context) {
-                                return SimpleDialog(
-                                  children: [
-                                    Padding(
-                                      padding: const EdgeInsets.all(16),
+                                return AlertDialog(
+                                  content: SingleChildScrollView(
                                     child: Text(licenseText),
                                   ),
+                                  actions: [
+                                    TextButton(
+                                      onPressed: () {
+                                        Navigator.of(context).pop();
+                                      },
+                                      child: Text(t.about.close),
+                                    ),
                                   ],
                                 );
                               },