Fix Example with Completed and Succeeded Execution Status

Today, an example `pipeline` that demonstrates using the execution
status of `tasks` - `$(tasks.status)` - in `when` expressions in
`finally tasks` uses `Succeeded` in a `Task` that should be executed
but the status is actually `Completed`. This example would be confusing
to users as reported on Slack.

As explained in the [docs](https://github.com/tektoncd/pipeline/blob/release-v0.24.x/docs/pipelines.md#using-aggregate-execution-status-of-all-tasks):
- `Succeeded`: all `tasks` have succeeded
- `Failed`: one ore more `tasks` failed
- `Completed`: all `tasks` completed successfully including one or more
skipped `tasks`

In this change:
- correct the `task` that should be executed to check `Completed`
instead of `Succeeded`
- add a `finally task` that shows `Succeeded` would block execution
because the aggregate execution status is actually `Completed`

examples/v1beta1/pipelineruns/pipelinerun-with-when-expressions.yaml

@@ -163,14 +163,24 @@ spec:
             - name: echo
               image: ubuntu
               script: exit 1
+      - name: finally-task-should-be-skipped-5 # when expression using tasks execution status, evaluates to false
+        when:
+          - input: "$(tasks.status)"
+            operator: in
+            values: ["Succeeded"]
+        taskSpec:
+          steps:
+            - name: echo
+              image: ubuntu
+              script: exit 1
       - name: finally-task-should-be-executed # when expression using execution status, tasks execution status, param, and results
         when:
           - input: "$(tasks.echo-file-exists.status)"
             operator: in
             values: ["Succeeded"]
           - input: "$(tasks.status)"
             operator: in
-            values: ["Succeeded"]
+            values: ["Completed"]
           - input: "$(tasks.check-file.results.exists)"
             operator: in
             values: ["yes"]