Remove provider courses page

[avinhurry]

Context

This page is old, we no longer link to it from anywhere, so we are getting rid of it.

Changes proposed in this pull request

Remove all related code.

Guidance to review

• Did I miss anything?
• Do you know of anywhere or anyone that uses this page?

Things to check

• If the code removes any existing feature flags, a data migration has also been added to delete the entry from the database
• This code does not rely on migrations in the same Pull Request
• If this code includes a migration adding or changing columns, it also backfills existing records for consistency
• If this code adds a column to the DB, decide whether it needs to be in analytics yml file or analytics blocklist, if included inform data insights team of the changes
• If this code adds a column that may include PII, the sanitise.sql script and 0025-protecting-personal-data-in-production-dump.md ADR have been updated
• API release notes have been updated if necessary
• If it adds a significant user-facing change, is it documented in the CHANGELOG?
• Attach the PR to the Trello card