Remove status messages about exams

[annagav]

Pre-Flight checklist

• [ ] Screenshots and design review for any changes that affect layout or styling
  • [x] Desktop screenshots
  • [ ] Mobile width screenshots
• [ ] Testing
  • [ ] Code is tested
  • [x] Changes have been manually tested

What are the relevant tickets?

Fix https://github.com/mitodl/micromasters/issues/5277

What's this PR do?

Remove status messages from the dashboard that are about exams. Weather passed, failed, about coming up future exams, about eligibility to take an exam.

How should this be manually tested?

There are way too many cases to test this manually.

On master, if you have passed a course run and there exists an exam run then you should be able to see a message about exam. On this branch you should see only messages about the course itself.

[codecov-commenter]

Codecov Report

Merging #5278 (3458cb1) into master (89d66f7) will decrease coverage by 0.03%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5278      +/-   ##
==========================================
- Coverage   93.68%   93.65%   -0.04%     
==========================================
  Files         501      501              
  Lines       23294    23125     -169     
  Branches      967      967              
==========================================
- Hits        21823    21657     -166     
+ Misses       1364     1361       -3     
  Partials      107      107              

Impacted Files	Coverage Δ
.../js/components/dashboard/courses/StatusMessages.js	93.81% <100.00%> (+1.13%)	:arrow_up:
...omponents/dashboard/courses/StatusMessages_test.js	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.