[CQ] migrate off deprecated Messages.OK_BUTTON (#8129)

Move off deprecated `Messages` constant.

See:
https://github.com/JetBrains/intellij-community/blob/master/platform/platform-api/src/com/intellij/openapi/ui/Messages.java

`Messages.getOkButton()` is the future.


---

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portions to this PR.

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Author: pq

flutter-idea/src/io/flutter/run/LaunchState.java

@@ -208,7 +208,7 @@ protected void showNoDeviceConnectedMessage(Project project) {
       project,
       "No connected devices found; please connect a device, or see flutter.dev/setup for getting started instructions.",
       "No Connected Devices Found",
-      new String[]{Messages.OK_BUTTON}, 0, AllIcons.General.InformationDialog);
+      new String[]{Messages.getOkButton()}, 0, AllIcons.General.InformationDialog);
   }
 
   @NotNull