[verifier] migrate off to-be-removed Messages API (#8776)

Slated for removal as of 2026.1.

In this case we can just go right to the `MessagesService` API this
convenience wrapper was delegating to.

<img width="1936" height="606" alt="image"
src="https://github.com/user-attachments/assets/72e03f46-f86f-4176-8377-0bd1110118e0"
/>

See: #8764



---

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portions to this PR.

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Author: pq

src/io/flutter/FlutterMessages.java

@@ -9,7 +9,7 @@
 import com.intellij.notification.NotificationType;
 import com.intellij.notification.Notifications;
 import com.intellij.openapi.project.Project;
-import com.intellij.openapi.ui.Messages;
+import com.intellij.openapi.ui.messages.MessagesService;
 import icons.FlutterIcons;
 import org.jetbrains.annotations.Nls;
 import org.jetbrains.annotations.NotNull;
@@ -54,8 +54,9 @@ public static int showDialog(@Nullable Project project,
                                @NotNull @Nls String title,
                                @NotNull String[] options,
                                int defaultOptionIndex) {
-    return Messages.showIdeaMessageDialog(project, message, title,
-                                          options, defaultOptionIndex,
-                                          FlutterIcons.Flutter_2x, null);
+    return MessagesService.getInstance()
+      .showMessageDialog(project, null, message, title,
+                         options, defaultOptionIndex, -1,
+                         FlutterIcons.Flutter_2x, null, true, null);
   }
 }