[Windows Arm64] Run plugin test post-submit (#141987)

The Flutter try pool does not have any Windows Arm64 machines. Thus, any Windows Arm64 pre-submit tests will fail as there's no machines to run them.

This converts the only Windows Arm64 pre-submit test, the plugin test, to run post-submit.

See: https://github.com/flutter/flutter/issues/141986

.ci.yaml

@@ -5396,6 +5396,7 @@ targets:
   - name: Windows_arm64 plugin_test_windows
     recipe: devicelab/devicelab_drone
     bringup: true # https://github.com/flutter/flutter/issues/134083
+    presubmit: false
     timeout: 60
     properties:
       dependencies: >-