Fix acceptance test assertions for updated plugin remove (#17126)

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

Author: donoghuc

qa/acceptance/spec/shared_examples/cli/logstash-plugin/remove.rb

@@ -33,7 +33,7 @@
     context "when the plugin isn't installed" do
       it "fails to remove it" do
         result = logstash.run_sudo_command_in_path("bin/logstash-plugin remove logstash-filter-qatest")
-        expect(result.stderr).to match(/This plugin has not been previously installed/)
+        expect(result.stderr).to include("The plugin `logstash-filter-qatest` has not been previously installed")
       end
     end