Announce rights for #core-ai

[JeffPaul]

Related to the new ​AI team announcement, please ensure that the following team members have access to announce /here in the #core-ai channel:
@flixos90
@isotropic
@jeffpaul
@swissspidy

[ryelle]

@flixos90, @jeffpaul, & @swissspidy should already have this, since it inherits from the #core access you all have. You can test it out by sending /here with no content, it'll tell you if you have access or not.

The channel needs to be added to https://meta.trac.wordpress.org/browser/sites/trunk/common/includes/slack/announce/config.php to show up in that access list, and @isotropic needs to be added. Unfortunately I'm still waiting on my access being restored, so I can't make the change.

[coffee2code]

In 14458:

Slack: Grant initial announce privileges for new #core-ai.

Props ryelle, JeffPaul.
Fixes #7988.