Use new OLL column for secondary topic; fix semester capitalization mismatch

[mbertrand]

What are the relevant tickets?

• Closes https://github.com/mitodl/hq/issues/5379
• Closes https://github.com/mitodl/hq/issues/5380

Description (What does it do?)

• Update the OLL ETL pipeline to use a new column in the google sheet for secondary topics (and updates the downloaded csv included in the repo)
• Update learning_resources.utils.get_year_and_semester and learning_resources.constants.semester_mapping so that semester values are consistently capitalized.

How can this be tested?

Run the following, it should complete without errors:

./manage.py backpopulate_oll_data

You can also try this to ingest directly from the google sheet instead of the csv provided in this repo:

./manage.py backpopulate_oll_data --sheets_id 1bWS-mqmuVraseMfY2YRu6gRnhXnjAS2N8CLiw4Tl8PE

Afterwards make sure that 60 results are returned at http://open.odl.local:8062/search/?platform=oll and that the OCW courses ingested from OLL all have capitalized first letters in their semester values.

[abeglova]

LGTM