Remove unused _build parameter from pipeline_execution_policy_build?
What does this MR do and why?
Removes the unused _build parameter from the pipeline_execution_policy_build? method in the SetBuildSources class.
The parameter was prefixed with an underscore to indicate it was unused, but since it's not needed, we can remove it entirely to clean up the code.
The scan_execution_policy_build? method still uses the _build parameter in the EE override, so it is kept.
Related to
Closes #584326
Follow-up from !209673 (merged)