docs: remove related documentation section from upgrading guide

- Remove outdated links section from docs/upgrading-spec-kit.md
- Remove outdated section from README and docs/index

Commit-generated-by: GitHub Copilot <github.copilot@github.com>
Signed-off-by: Ashley Childress <6563688+anchildress1@users.noreply.github.com>

Author: anchildress1

README.md

@@ -308,9 +308,6 @@ If you encounter issues with an agent, please open an issue so we can refine the
 
 ## 📖 Learn More
 
-- **[Installation Guide](./docs/installation.md)** - First-time installation instructions
-- **[Quick Start Guide](./docs/quickstart.md)** - Get started with a new project
-- **[Upgrading Spec Kit](./docs/upgrading-spec-kit.md)** - Update CLI and project files
 - **[Complete Spec-Driven Development Methodology](./spec-driven.md)** - Deep dive into the full process
 - **[Detailed Walkthrough](#-detailed-process)** - Step-by-step implementation guide
 

docs/index.md

@@ -8,13 +8,6 @@
 
 Spec-Driven Development **flips the script** on traditional software development. For decades, code has been king — specifications were just scaffolding we built and discarded once the "real work" of coding began. Spec-Driven Development changes this: **specifications become executable**, directly generating working implementations rather than just guiding them.
 
-## Getting Started
-
-- [Installation Guide](installation.md) - First-time installation of Spec Kit
-- [Quick Start Guide](quickstart.md) - Start a new project with Spec Kit
-- [Upgrading Spec Kit](upgrading-spec-kit.md) - Update CLI and project files
-- [Local Development](local-development.md) - Contribute to Spec Kit development
-
 ## Core Philosophy
 
 Spec-Driven Development is a structured process that emphasizes:

docs/upgrading-spec-kit.md

@@ -434,12 +434,3 @@ After upgrading:
 - **Review release notes:** Check [GitHub Releases](https://github.com/github/spec-kit/releases) for new features and breaking changes
 - **Update workflows:** If new commands were added, update your team's development workflows
 - **Check documentation:** Visit [github.io/spec-kit](https://github.github.io/spec-kit/) for updated guides
-
----
-
-## Related Documentation
-
-- [Installation Guide](installation.md) - First-time setup instructions
-- [Existing Project Guide](existing-project-guide.md) - Adding Spec Kit to existing codebases
-- [Quick Start](quickstart.md) - Getting started with new projects
-- [Local Development](local-development.md) - Contributing to Spec Kit itself