Remove obsolete dependencies

[nvloff-f3]

• [ ] github.com/aholic/ggtimer
  • [ ] #193
• [ ] github.com/chobie/go-gaussian
• [ ] github.com/hako/durafmt
• [x] Remove github.com/phayes/freeport
  • [x] #169
• [x] Remove github.com/pkg/errors
  • [x] #160
• [x] Replace https://github.com/giantswarm/retry-go with https://github.com/avast/retry-go
  • [x] #161
• [x] Remove https://github.com/asaskevich/govalidator
  • [x] #163
• [x] Remove https://github.com/workanator/go-ataman
  • [x] #181