vendor/github.com/mndrix/tap-go: Bump to 629fa40

To pick up t.YAML(...) for more visible error messages.  See ad47e7d
(Makefile: Change from prove to node-tap, 2017-11-30, opencontainers#439) about how
node-tap handles YAML blocks vs. diagnostics.

Generated with:

  $ go get -u github.com/mndrix/tap-go
  $ godep update github.com/mndrix/tap-go
  $ emacs Godeps/Godeps.json  # remove gopkg.in/yaml.v2 entry
  $ rm -rf vendor/gopkg.in/yaml.v2
  $ git add vendor/github.com/mndrix

We don't need gopkg.in/yaml.v2 because we're using tap-go's JSON
output.

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking