toolchain-utils: update skylab credential location for role account

The skylab credential has been checked into crostc. This patch updates
the location of the json file.

TEST=Tested with skylab dut using role account.
BUG=chromium:984790

Change-Id: I163b6aef14bc7df8c85e556032455a7cc7d7822d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1838442
Tested-by: Zhizhou Yang <zhizhouy@google.com>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Commit-Queue: Zhizhou Yang <zhizhouy@google.com>
1 file changed