Revert "gemspec: fix io-event and io-stream version to avoid unstable behavior on Windows (#5042)" (#5078)

**Which issue(s) this PR fixes**: 
* Related to #5041

**What this PR does / why we need it**: 
This reverts commit 420e166.

85740ac should resolve the fundamental
issue.

**Docs Changes**:
Not needed.

**Release Note**: 
CI fixes.

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Author: daipom

fluentd.gemspec

@@ -42,13 +42,6 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency("uri", '~> 1.0')
   gem.add_runtime_dependency("async-http", "~> 0.86")
 
-  # It appears io-event >= 1.11.0 are unstable on Windows (confirmed on 1.12.1 or lower).
-  # See https://github.com/fluent/fluentd/issues/5041.
-  gem.add_runtime_dependency("io-event", "< 1.11.0")
-  # io-stream >= 0.8 needs io-event >= 1.12.0, so we need to fix io-stream version as well (confirmed on 0.10.0 or lower).
-  # See https://github.com/socketry/io-stream/issues/8.
-  gem.add_runtime_dependency("io-stream", "< 0.8.0")
-
   # gems that aren't default gems as of Ruby 3.4
   gem.add_runtime_dependency("base64", ["~> 0.2"])
   gem.add_runtime_dependency("csv", ["~> 3.2"])