Link troubleshooting doc to Web IDE error page

Issue: Add admin docs for handling Web IDE Oauth misco... (#474899 - closed)

What does this MR do and why?

This MR links the troubleshooting doc added in Add Web IDE OAuth misconfiguration troubleshoot... (!166048 - merged) to the Web IDE OAuth misconfiguration error page as per the guidelines.

Screenshots or screen recordings

How to set up and validate locally

• Apply the following patch to render the error page on every Web IDE load:

  diff --git a/app/assets/javascripts/ide/index.js b/app/assets/javascripts/ide/index.js
  index 4b856550f2b9..aa32ffb4cc86 100644
  --- a/app/assets/javascripts/ide/index.js
  +++ b/app/assets/javascripts/ide/index.js
  @@ -35,10 +35,10 @@ export async function startIde(options) {
   
     const oAuthCallbackDomainMismatchApp = new OAuthCallbackDomainMismatchErrorApp(ideElement);
   
  -  if (oAuthCallbackDomainMismatchApp.shouldRenderError()) {
  -    oAuthCallbackDomainMismatchApp.renderError();
  -    return;
  -  }
  +  // if (oAuthCallbackDomainMismatchApp.shouldRenderError()) {
  +  oAuthCallbackDomainMismatchApp.renderError();
  +  return;
  +  // }
     const { initGitlabWebIDE } = await import('./init_gitlab_web_ide');
     initGitlabWebIDE(ideElement);
   }
  

• In the GDK, open a Web IDE in a project.

• You should see the error page with the new Learn more link.