[v13.0.0-beta.0] Dropdown div transition is broken

[microbit-robert]

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Description

The Blockly dropdown div no longer smoothly appears when it is triggered (transform and opacity). It simply appears and disappears with no transition at all. Comparison in videos below.

Reproduction steps

Priority

No response

Stack trace

Screenshots

Previous version, with transition:
https://github.com/user-attachments/assets/487e2f20-53e1-4be5-b62c-074c9dfb8f7d

v13, without transition:
https://github.com/user-attachments/assets/aa35745c-f544-4c47-abc9-f30adda263d8

Browsers

No response