fix(ci): remove GA expression from npm script

- Change optimize script to 'jampack _site' to avoid shell bad substitution in Actions
- GitHub Actions expressions are not interpolated inside package.json scripts
- Workflow already outputs site to _site

Author: yunseo-kim

package.json

@@ -3,7 +3,7 @@
     "@divriots/jampack": "^0.33.1"
   },
   "scripts": {
-    "optimize": "jampack _site${{ steps.pages.outputs.base_path }}",
+    "optimize": "jampack _site",
     "cleanAllDotJampack": "find -s . | grep '.jampack$' | xargs rm -fr"
   },
   "engines": {