Remove unused auth credentials

Remove configurations for GDS SSO and CDDO SSO auth providers.

We completed migrating from GDS SSO to Auth0 some time ago, and have no
need to revert now.

We only ever tested CDDO SSO in the user research environment, and
haven't used it for some time.

So we can remove the code for these safely.

Author: lfdebrux

infra/modules/forms-admin/main.tf

@@ -26,26 +26,6 @@ locals {
         valueFrom = "arn:aws:ssm:eu-west-2:${data.aws_caller_identity.current.account_id}:parameter/forms-admin-${var.env_name}/auth/password"
       }
     ],
-    gds_sso = [
-      {
-        name      = "GDS_SSO_OAUTH_ID",
-        valueFrom = "arn:aws:ssm:eu-west-2:${data.aws_caller_identity.current.account_id}:parameter/forms-admin-${var.env_name}/gds-sso-oauth-id"
-      },
-      {
-        name      = "GDS_SSO_OAUTH_SECRET",
-        valueFrom = "arn:aws:ssm:eu-west-2:${data.aws_caller_identity.current.account_id}:parameter/forms-admin-${var.env_name}/gds-sso-oauth-secret"
-      }
-    ],
-    cddo_sso = [
-      {
-        name      = "SETTINGS__CDDO_SSO__IDENTIFIER",
-        valueFrom = "arn:aws:ssm:eu-west-2:${data.aws_caller_identity.current.account_id}:parameter/forms-admin-${var.env_name}/cddo-sso/identifier"
-      },
-      {
-        name      = "SETTINGS__CDDO_SSO__SECRET",
-        valueFrom = "arn:aws:ssm:eu-west-2:${data.aws_caller_identity.current.account_id}:parameter/forms-admin-${var.env_name}/cddo-sso/secret"
-      }
-    ],
     auth0 = [
       {
         name      = "SETTINGS__AUTH0__CLIENT_ID",