Replace password with API key in Jenkins setup (#1731)
Replace password with API key in Jenkins setup (#1731)

The documentation mentioned that the Jenkins master should be set up
using a user's password. It turns out that the API key should be used
instead. This commit changes the documentation to reflect that.

Co-authored-by: Michael Plump <25c2b4883978f4264609c4519fcccd0292e25509@google.com>
ttomsu/spinnaker.github.io,ttomsu/spinnaker.github.io,spinnaker/spinnaker.github.io,ttomsu/spinnaker.github.io,spinnaker/spinnaker.github.io,spinnaker/spinnaker.github.io