CI: Install io-event error on Ruby HEAD

[Watson1978]

Describe the bug

When install io-event gem with Ruby HEAD, it causes error.
See https://github.com/fluent/fluentd/actions/runs/15807521873/job/44554393822

To Reproduce

Run Test with Ruby head workflow

Expected behavior

No error

Your Environment

- Fluentd version:
- Package version:
- Operating system:
- Kernel version:

Your Configuration

none

Your Error Log

See above

Additional context

No response

[Watson1978]

Reported to socketry/io-event#141

[daipom]

Thanks!!

[Watson1978]

This issue can be closed when socketry/io-event#142 was merged and released.

[Watson1978]

This issue was solved at upstream.

However, tests with Ruby HEAD still have the failures.
https://github.com/fluent/fluentd/actions/runs/16038990708/job/45256769355

But, it is other problem. I will file the problem with new ticket.

[daipom]

Thanks!

[Watson1978]

However, tests with Ruby HEAD still have the failures. https://github.com/fluent/fluentd/actions/runs/16038990708/job/45256769355

Seems it is same failures with #5009