fix(skill): clean up bmad-sprint-planning validation findings

Remove installed_path and unused intra-skill path variables from
workflow.md (PATH-02, PATH-04).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/bmm/workflows/4-implementation/bmad-sprint-planning/workflow.md

@@ -21,9 +21,6 @@ Load config from `{project-root}/_bmad/bmm/config.yaml` and resolve:
 
 ### Paths
 
-- `installed_path` = `.`
-- `template` = `{installed_path}/sprint-status-template.yaml`
-- `checklist` = `{installed_path}/checklist.md`
 - `tracking_system` = `file-system`
 - `project_key` = `NOKEY`
 - `story_location` = `{implementation_artifacts}`