docs/builder: fix typo
docs/builder: fix typo

Signed-off-by: Eric Engestrom <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@engestrom.ch>

cpuguy83/cli,cpuguy83/cli,thaJeztah/cli,docker/cli,docker/cli,thaJeztah/cli