Revert "Add client_auth_method test cases for OIDC"

This reverts commit f280cc1c.

Previously, rack-oauth2 only accepted Symbols for client_auth_method.
Commit f280cc1c worked around this by converting the String type to
a Symbol and forwarding it.

As of 1.14.0, rack-oauth2 accepts both data types. With the version bump
to 1.16.0, the workaround that was in place can now be removed.
Signed-off-by: Vincent Fazio <vfazio@xes-inc.com>

spec/lib/gitlab/omniauth_initializer_spec.rb

@@ -101,33 +101,5 @@ RSpec.describe Gitlab::OmniauthInitializer do
 
       subject.execute([google_config])
     end
-
-    it 'converts client_auth_method to a Symbol for openid_connect' do
-      openid_connect_config = {
-        'name' => 'openid_connect',
-        'args' => { name: 'openid_connect', client_auth_method: 'basic' }
-      }
-
-      expect(devise_config).to receive(:omniauth).with(
-        :openid_connect,
-        { name: 'openid_connect', client_auth_method: :basic }
-      )
-
-      subject.execute([openid_connect_config])
-    end
-
-    it 'converts client_auth_method to a Symbol for strategy_class OpenIDConnect' do
-      openid_connect_config = {
-        'name' => 'openid_connect',
-        'args' => { strategy_class: OmniAuth::Strategies::OpenIDConnect, client_auth_method: 'jwt_bearer' }
-      }
-
-      expect(devise_config).to receive(:omniauth).with(
-        :openid_connect,
-        { strategy_class: OmniAuth::Strategies::OpenIDConnect, client_auth_method: :jwt_bearer }
-      )
-
-      subject.execute([openid_connect_config])
-    end
   end
 end