Update gem version to 2.6.6.1 for release
Update gem version to 2.6.6.1 for release

appneta/ruby-traceview,tlunter/oboe-ruby,appneta/ruby-traceview,tlunter/oboe-ruby,boyang-li/oboe-ruby,boyang-li/oboe-ruby,tlunter/oboe-ruby,tlunter/oboe-ruby,appneta/ruby-traceview,boyang-li/oboe-ruby,appneta/ruby-traceview,boyang-li/oboe-ruby