GitLab CI/CD Guide is out of date

[jkodroff]

https://www.pulumi.com/docs/iac/using-pulumi/continuous-delivery/gitlab-ci/

This page is out of date. Here's what should change:

• We need to ensure that the screenshot shows the new Merge Request comments, per this blog post: https://www.pulumi.com/blog/gitlab-better-than-ever/
• The example should highlight using ESC to grab OIDC creds instead of scripting aws in bash, at least as a first option. We can keep the bash scripting to get AWS creds, but I might make it an appendix or something less prominent.
• Links to Organizational Templates, which is also missing information on GitLab. See Organizational Templates lack documentation on how to use with GitLab #14427
• @dschaller Can you confirm that a bash script is still the best we can do as far as orchestration of the actual CI/CD steps, and that we have yet to develop the GL equivalent of a GH action? (No shade - I know that the ecosystem may not be as easy for us to develop a solution for.)

This should be addressed alongside #12515 if there's anything additional actionable in the aforementioned issue - I would just make sure it's clear which steps are in the GL UI.