Update Dev on-call process

What is changing?

This MR removes the Development Escalation Process documentation, effective January 5th, 2025. The process is being discontinued and replaced with the Tier 2 On-Call Program for technical support escalations.

Why is this change being made?

The Dev Escalation process was originally established to provide Rails Monolith support to the Infrastructure department. However, over time several factors have made this process less effective:

1. Scope expansion: The responsibilities expanded beyond the original intent to include general application support for both Infrastructure and Support teams, as well as the Master Broken process (which has recently changed).

2. Expertise mismatch: The GitLab application has become so broad that it's unlikely the on-call engineer will have expertise in the specific area that needs attention during an escalation.

3. Better alternative available: The introduction of the Tier 2 On-Call Program now provides access to Subject Matter Experts who are better positioned to handle specific technical issues.

This change streamlines our escalation process by directing teams to use the more appropriate Tier 2 On-Call Program instead of maintaining a parallel, less effective process.

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