Remove reference to bower in UI README (#5137)
Remove reference to bower in UI README (#5137)

@meirish removed Bower in #4526 but the references to it in the README
were still intact.
kingland/vault,hartsock/vault,kingland/vault,quixoten/vault,hartsock/vault,quixoten/vault,hashicorp/vault,kingland/vault,joelthompson/vault,rnaveiras/vault,hashicorp/vault,hashicorp/vault,hartsock/vault,rnaveiras/vault,kingland/vault,hartsock/vault,hashicorp/vault,quixoten/vault,hashicorp/vault,hartsock/vault,kingland/vault,joelthompson/vault,joelthompson/vault,rnaveiras/vault,rnaveiras/vault,joelthompson/vault,rnaveiras/vault,hashicorp/vault,quixoten/vault