Relax limitation of bundler version

There is no need to cap ceiling.

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

fluent-plugin-watch-objectspace.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = test_files
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", [">= 2.2.33", "< 2.6"]
+  spec.add_development_dependency "bundler", [">= 2.2.33"]
   spec.add_development_dependency "rake", "< 14"
   spec.add_development_dependency "test-unit", "< 3.7"
   spec.add_development_dependency "test-unit-rr", "< 1.1"