remove calls to Step.closeout in tests

[braingram]

Several tests call Step.closeout with no arguments. This results in a single call to gc.collect (since both to_close and to_del were not provided).

This PR removes the calls to Step.closeout. These were not replaced with calls to gc.collect (as python should manage that itself). Removing the usage in the tests will allow Step.closeout to be removed (as it is otherwise unused).

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 57.93%. Comparing base (6580914) to head (781e0e0).
Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8428      +/-   ##
==========================================
+ Coverage   56.38%   57.93%   +1.55%     
==========================================
  Files         387      387              
  Lines       38716    38839     +123     
==========================================
+ Hits        21830    22502     +672     
+ Misses      16886    16337     -549     

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[hbushouse]

Looks OK to me.