Remove vestigial SAML references

[brodygov]

The dashboard switched from SAML to OIDC a year ago, but still has a lot of references to SAML in disabled tests and in dependencies.

bac2d0e

We should ideally replace these tests with relevant tests for OIDC and remove all the unused references to SAML.

There are a number of config variables that refer to SAML when they are actually used for OIDC.

• saml_sp_private_key is actually used for OIDC
• saml_sp_certificate is not used, since OIDC doesn't use certificates, but it's required by config/initializers/figaro.rb