Stop regenerating gh-pages index.md in release script

Hugo on `main` now owns the Pages index, so the release script no
longer needs to write a Jekyll front-matter wrapper around README.md
on the gh-pages branch. The phpDocumentor block that builds and
publishes `doc/$tag/` is unchanged — that versioned tree continues to
live on gh-pages and is preserved by the new workflow's
`keep_files: true`.

For STF-448.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: oschwald

dev-bin/release.sh

@@ -168,19 +168,6 @@ php phpDocumentor.phar \
 
 rm -rf "$cachedir"
 
-page=index.md
-cat <<EOF >$page
----
-layout: default
-title: MaxMind GeoIP2 PHP API
-language: php
-version: $tag
----
-
-EOF
-
-cat ../README.md >>$page
-
 git add doc/
 
 echo "Release notes for $tag:"