[Cinder] Extending Specs Freeze Deadline to Jun 7

Hello,

As discussed in the last cinder meeting [1] we are extending the cinder specs freeze deadline to June 7. The previous week contains holidays for some on our team, so the weekend days are added to make sure everything that needs to merge has sufficient time to do so.

Please make sure your specs are updated before the new deadline.

[1]: https://meetings.opendev.org/meetings/cinder/2024/cinder.2024-06-26-14.00.lo...

Thanks,