Increase period before merging broken MRs is allowed

Why is this change being made?

Two hours feels a little bit too short. The SLOs for broken master are four hours for triage, and four hours for resolution (eight hours total), so picking a period that's equal to those seems like it makes sense.

Does this MR meet the acceptance criteria?

Assign to DRI

• Did you assign this change to the correct DRI of the page or information you are changing?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what