Fix acceptance test assertions for updated plugin remove

[donoghuc]

Release notes

[rn:skip]

What does this PR do?

This commit updates the acceptance tests to expect messages in the updated format for removing plugins. See #17030 for change.

Why is it important/What is the impact to the user?

No user impact, this is fixing acceptance test assertions

Checklist

• My code follows the style guidelines of this project
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
  - [ ] I have added tests that prove my fix is effective or that my feature works

Related issues

• Relates to plugins: improve remove command to support multiple plugins #17030
• Completes Fix acceptance test assertions for updated plugin remove #17122

Logs

Example failures:
https://buildkite.com/elastic/logstash-exhaustive-tests-pipeline/builds/1361#01952103-6591-43cf-a364-cc876ac8bc21

Failures:
--
  |  
  | 1) CLI operation behaves like logstash remove logstash-plugin remove on [Ubuntu 20.04] when the plugin isn't installed fails to remove it
  | Failure/Error: DEFAULT_FAILURE_NOTIFIER = lambda { \|failure, _opts\| raise failure }
  |  
  | expected "ERROR: Operation aborted, cannot remove plugin, message: The plugin `logstash-filter-qatest` has not been previously installed" to match /This plugin has not been previously installed/
  | Diff:
  | @@ -1 +1 @@
  | -/This plugin has not been previously installed/
  | +"ERROR: Operation aborted, cannot remove plugin, message: The plugin `logstash-filter-qatest` has not been previously installed"
  |  
  | Shared Example Group: "logstash remove" called from ./acceptance/spec/lib/cli_operation_spec.rb:38
  | # ./acceptance/spec/shared_examples/cli/logstash-plugin/remove.rb:36:in `block in <main>'
  | # ./Rakefile:30:in `block in <main>'
  |  
  | Finished in 20 minutes 37 seconds (files took 1.57 seconds to load)
  | 30 examples, 1 failure, 1 pending

[mashhurs]

LGTM!

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 01ad2ef

[donoghuc]

@logstashmachine backport 9.0

[donoghuc]

@logstashmachine backport 8.x