docs(skills): drop hand-copied naming rules from gh-skill

Avoids drift between this skill and the actual validation logic in
publish. Agents should run `gh skill publish --dry-run` to learn the
current rules from the source of truth.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

skills/gh-skill/SKILL.md

@@ -82,14 +82,6 @@ license: MIT                  # optional but recommended
 ---
 ```
 
-Naming rules (enforced by `publish`):
-
-- Lowercase alphanumeric and hyphens only, 1-64 chars.
-- Must start and end with `[a-z0-9]`.
-- No double hyphens (`--`).
-- `allowed-tools`, if present, must be a string (space-delimited), not a
-  YAML array.
-
 ### Validate, then publish
 
 ```bash