Update docs/upgrade.md

In the Quick Reference table, the label “pipx upgrade” is misleading because the command shown is `pipx install --force ...` (a reinstall). by copilot.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: D7x7z49

docs/upgrade.md

@@ -9,7 +9,7 @@
 | What to Upgrade | Command | When to Use |
 |----------------|---------|-------------|
 | **CLI Tool Only** | `uv tool install specify-cli --force --from git+https://github.com/github/spec-kit.git@vX.Y.Z` | Get latest CLI features without touching project files |
-| **pipx upgrade** | `pipx install --force git+https://github.com/github/spec-kit.git@vX.Y.Z` | Upgrade pipx-installed CLI |
+| **CLI Tool Only (pipx)** | `pipx install --force git+https://github.com/github/spec-kit.git@vX.Y.Z` | Reinstall/upgrade a pipx-installed CLI to a specific release |
 | **Project Files** | `specify init --here --force --ai <your-agent>` | Update slash commands, templates, and scripts in your project |
 | **Both** | Run CLI upgrade, then project update | Recommended for major version updates |