If there is no name argument given, OmniAuth will try to guess the name
by the class name. In
https://github.com/omniauth/omniauth/blob/v1.9.0/lib/omniauth/strategy.rb#L139,
`OmniAuth::Strategies::OpenIDConnect` gets translated to
`openidconnect`.

This leads to an immediate 404 error after clicking the login button
because OmniAuth can't match the current route (/users/auth/openid_connect)
against the expected one (/users/auth/openidconnect).

Other providers, such as Google OAuth2, set this name as the default
option within the OmniAuth Strategy. Until a fix is merged upstream,
let's just set the parameter ourselves.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/62208