Have uniform date styling on Program page.

[collinpreston]

Pre-Flight checklist

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

What are the relevant tickets?

https://github.com/mitodl/micromasters/issues/5254

What's this PR do?

Makes sure that all the dates on the program pages are formatted the same way (DD-MMM-YYYY).

How should this be manually tested?

1. Have your micromasters up and running with a staff user that you can login with.
2. Seed your database or create courses, course runs (that start in the future), and a program which references your created courses. It would be best to pick different months for the start dates of each course run.
3. Access CMS (http://mm.odl.local:8079/) and add a child page (Program page) to the main page.
4. Set the program field to the program you created in step 2.
5. Add two or more program courses that you created in step 2.
6. Create a couple future semesters with a random title and a date set in the future.
7. Publish the program page.
8. Within CMS, click the "View Live" button on the program page you published in step 7.
9. Verify that all of the dates shown in the "Courses" and "Future Courses" list sections only show 3 letters for the month.

Any background context you want to provide?

Helpful resources:

• https://docs.djangoproject.com/en/dev/ref/templates/builtins/#date. This resource explains the different characters you can define in your date format specification and what they do.
• https://stackoverflow.com/questions/15378537/django-python-showing-months-in-words-instead-of-numbers. The answer to this question showed me that I could just add styling to the template and at the specific field I wanted to using |date

Screenshots (if appropriate)

[codecov-commenter]

Codecov Report

Merging #5266 (d483a70) into master (22fde05) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5266   +/-   ##
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  Coverage   93.68%   93.68%           
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  Files         501      501           
  Lines       23273    23273           
  Branches      965      965           
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  Hits        21804    21804           
  Misses       1362     1362           
  Partials      107      107           

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