ci-operator/step-registry/ipi/deprovision/artifacts/bootstrap: Drop gather

The installer does this automatically since
openshift/installer@cad7f02a8b (cmd: gather the logs from bootstrap
instead of printing commands, 2019-06-05, openshift/installer#1822).
You'd still need to SSH in to gather manually in 4.1.z, but if we
think that's important we should backport the gather logic to the
installer's 4.1 branch [1].

[1]: openshift/installer#2840

Author: wking

ci-operator/step-registry/ipi/deprovision/artifacts/bootstrap/OWNERS

@@ -2,7 +2,6 @@ chain:
   as: ipi-deprovision-artifacts
   steps:
   - ref: ipi-deprovision-artifacts-artifacts
-  - ref: ipi-deprovision-artifacts-bootstrap
   - ref: ipi-deprovision-artifacts-must-gather
   documentation: |-
-    The IPI deprovision artifacts step chain contains all the individual steps necessary to collect artifacts from a cluster.
+    The IPI deprovision artifacts step chain contains all the individual steps necessary to collect artifacts from a cluster.