Update metadata to use correct copyright

Author: gesa

package.json

@@ -10,7 +10,7 @@
     "build-only": "ecmarkup --verbose spec.html --multipage out",
     "build": "npm run build-head",
     "build-for-pdf": "npm run prebuild-only && ecmarkup --verbose spec.html out/index.html --assets external --assets-dir out --printable --lint-spec --strict",
-    "pdf": "npm run build-for-pdf && prince --script ./node_modules/ecmarkup/js/print.js out/index.html -o out/ECMA-262.pdf",
+    "pdf": "npm run build-for-pdf && prince-books --script ./node_modules/ecmarkup/js/print.js out/index.html -o out/ECMA-262.pdf",
     "prebuild-snapshot": "npm run clean",
     "build-snapshot": "npm run build-head && node scripts/insert_snapshot_warning.js",
     "clean": "rm -rf out",

spec.html

@@ -158,6 +158,8 @@
   status: draft
   location: https://tc39.es/ecma262/
   markEffects: true
+  boilerplate:
+    copyright: alternative
 </pre>
 <p><img src="img/ecma-logo.svg" id="ecma-logo" alt="Ecma International logo"></p>
 <div id="metadata-block">