Bump cmetrics version to latest (0.3.3)

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

Author: kenhys

fluent-plugin-node-exporter-metrics.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = test_files
   spec.require_paths = ["lib"]
 
-  spec.add_runtime_dependency "cmetrics", "~> 0.2.3"
+  spec.add_runtime_dependency "cmetrics", "~> 0.3.3"
   spec.add_runtime_dependency "capng_c", "~> 0.2.2"
 
   spec.add_development_dependency "bundler", "~> 2.2.0"