dev/ci: set -e on asdf-install.sh
Created by: bobheadxi
Looks like asdf-install.sh does not fail with a non-zero exit code if installation fails? https://buildkite.com/sourcegraph/sourcegraph/builds/147001#dd36d5f3-b7d7-45ba-aa43-d2bd3b6e39d6/141-163
Test plan
CI passes