revert: "fix(ops/pipelines): Remove duplicated wait step"

This reverts commit 5e036ed9fc.

Reason for revert: This introduced a logic error since the remaining
step runs at the wrong point in the pipeline. Temporarily reverting to
having duplicated waits in order to clean up later.

Change-Id: Ifa6ece50dd22924f02efd7b790a5863ca1189af7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4841
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>

ops/pipelines/static-pipeline.yaml

@@ -22,6 +22,10 @@ steps:
         buildkite-agent pipeline upload $$chunk
       done
 
+  # Wait for all previous steps to complete.
+  - wait: null
+    continue_on_failure: true
+
   # Exit with success or failure depending on whether any other steps
   # failed.
   #