Add Infradev triaging to CA reaction rotation

Why is this change being made?

Add Infradev triaging to CA reaction rotation to make sure we regularly check these issues.

The infradev process is a company wide initiative to better address issues related to availability and reliability of GitLab.com.

The catalyst for us adding this to our reaction rotation is the recent events that occured and required a rapid-action to be created and related discussion from Product in Product#2185 (closed). Even is Secure is very rarely (if not never) involved in such issues we must be cautious with these as they can have a big impact on our SAAS.

As infradev issues are not only bugs, they might not be caught in our bugs triage process, hence the need for this additional issues board to be checked.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the "Maintained by" section in on the page being edited.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files. (this requirement has been removed pending identification of a new DRI for the handbook)