Fix selector broken by case change in plugin

[fqueiruga]

postbuildscript-2.11.0 changed the string "Execute Scripts" to "Execute scripts" (see commit). This broke the following tests

• PostBuildScriptPluginTest#run_post_build_step
• PostBuildScriptPluginTest#skip_for_jobs_that_succeeded

This PR fixes the selector

[uhafner]

Wouldn't it be better to add both values (old and new) then the plugin tests will continue to work with the previous version as well?

[fqueiruga]

You're right, done.

[timja]

Wouldn't it be better to add both values (old and new) then the plugin tests will continue to work with the previous version as well?

not really sure why you would want to verify old versions of this plugin? unless it's core baseline is really new you would always be validating the latest version I would expect

[uhafner]

I don't know if that makes sense for that particular plugin. But in general, if the new release of this plugin requires a newer core version, then a depending plugin will still pick up the old version of the plugin in its UI tests.

[timja]

tests pass now https://ci.jenkins.io/job/Core/job/acceptance-test-harness/job/PR-622/2/testReport/plugins/PostBuildScriptPluginTest/