Remove routes and reference to school privacy policy in codebase

[MylesJarvis]

Trello card

• https://trello.com/c/TNWxAQUr

Merging blocked until the following ticket is complete:

• trello.com/c/UvYUca3d

Context

• We're amalgamating our privacy policies into the wider GIT policy.
• This now includes the Manage school experience privacy policy
• We need to now link to the main privacy policy once that amalgamation is complete

Changes proposed in this pull request

• remove references to school privacy policy in the code base
• links that previously went to schools privacy policy now go to the main privacy policy
• remove any if statements that changed behaviour relating to privacy policies when in the 'school namespace'

Guidance to review

• this does not have a redirect in place
• are we comfortable with this? I suspect direct landings on to that page are incredibly low

[gemmadallmandfe]

@MylesJarvis Thanks for doing this :-)

We will need to delete the old MSE privacy policy page app/views/pages/schools_privacy_policy.html.erb - think it is probably worth doing on this PR?

Otherwise looks good to me

[github-actions[bot]]

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