fix(ui5-button): remove reference to last clicked button

[didip1000]

Fixes: #11865

[didip1000]

I could not think of a valid test for this scenario as Cypress doesnt even have access to the variable, so the fix was only tested manually

[ui5-webcomponents-bot]

🚀 Preview deployment ready: https://UI5.github.io/webcomponents/pr-12370/

The preview will be updated automatically when you push new commits to this PR.

[tsanislavgatev]

Should we remove it at all or should we remove it only when destroyed? I remeber we had a conversation to remove it only when destroyed. Do we know why it was set there to remove it without more testing?

[ui5-webcomponents-bot]

🚀 Deployed on https://pr-12370--ui5-webcomponents-preview.netlify.app

[didip1000]

Should we remove it at all or should we remove it only when destroyed? I remeber we had a conversation to remove it only when destroyed. Do we know why it was set there to remove it without more testing?

As far as I've tested, it's used only to update the active property which is private and used to denote the active state of the button. In the CSS you can replace [active] with :active everywhere where it's used and the button, toggle button, and split button appear to continue working properly. I'm not sure why it was added in the first place (it was added a long time ago) and I could be missing something.

We discussed I think the possibility that it was used by the split button, but the split button has it's own activeArrowButton which doesn't seem related to this.