Fix duplicate word typo
Fix duplicate word typo

Removes the duplicate "system" word
faxriddin/build-web-application-with-golang,astaxie/build-web-application-with-golang,admpub/build-web-application-with-golang,admpub/build-web-application-with-golang,admpub/build-web-application-with-golang,WangKaimin/build-web-application-with-golang,faxriddin/build-web-application-with-golang,songqii/build-web-application-with-golang,astaxie/build-web-application-with-golang,admpub/build-web-application-with-golang,songqii/build-web-application-with-golang,WangKaimin/build-web-application-with-golang,astaxie/build-web-application-with-golang