How do I reclaim reserved space in the sysjobstepslogs table
You could try just rebuilding the table:

ALTER TABLE dbo.sysjobstepslogs REBUILD;


If you're on Enterprise (or Evaluation or Developer) you can do:

ALTER TABLE dbo.sysjobstepslogs REBUILD WITH (ONLINE = ON);


The table only has a single clustered index (PK_SomeAwfulGUID-basedName) and this rebuild operation should deallocate all of the pages that might still be associated with the table.