Remove deprecated builders.
Remove deprecated builders.

ironhide is no longer supported, and the board has been removed, so
remove the builders. Also remove deprecated corei7 informational
builder.

BUG=none
TEST=cbuildbot_config_unittest.py

Change-Id: I21350a58a7b466917fc09b9b2e96d5daeac413b5
Reviewed-on: https://gerrit.chromium.org/gerrit/27456
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: Peter Mayo <3d31fdaf44dc55bb1b4f50b19df9bc879177d37a@chromium.org>
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Commit-Ready: Peter Mayo <3d31fdaf44dc55bb1b4f50b19df9bc879177d37a@chromium.org>

bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite,coreos/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite