Fix impossible condition in bun setup-environment.sh

Remove check that combined mutually exclusive conditions (-z and -n
on the same variable), which could never evaluate to true.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: robertherber

skills/plugins/bun/scripts/setup-environment.sh

@@ -34,11 +34,6 @@ if [ -z "$BUN_VERSION" ] && [ -f "$PROJECT_DIR/.env.github" ]; then
   fi
 fi
 
-# 4. Check if already set in environment
-if [ -z "$BUN_VERSION" ] && [ -n "${BUN_VERSION:-}" ]; then
-  echo "🌍 Using BUN_VERSION from environment: $BUN_VERSION"
-fi
-
 check_bun_not_installed() {
   if command -v bun >/dev/null 2>&1; then
     local installed