Web IDL validation errors

[autokagami]

🤖 This is an automatic issue report for Web IDL validation error. 🤖

The bot found validation errors but couldn't fix them automatically, since the IDL texts include HTML tags. Please check the following messages and fix them.

• Validation error at line 27 in html,6:
    void showPopover();
    ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 28 in html,6:
    void hidePopover();
    ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

• Validation error at line 29 in html,6:
    void togglePopover(optional boolean
    ^
  

  Error: void is now replaced by undefined. Refer to the relevant GitHub issue for more information.

Please file an issue at https://github.com/saschanaz/webidl-updater/issues/new if you think this is invalid or should be enhanced.

[annevk]

I missed this. This got fixed by #8860.