SOLR-14024 Invalid html generated by changes2html.pl

[asalamon74]

Original lucene-solr pull request: apache/lucene-solr#1060

Description

changes2html.pl generates invalid html

Solution

Fix it to generate a valid html.

Tests

Created the html and tested it using https://validator.w3.org/

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Lucene maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.

[rmuir]

Thanks @asalamon74 ! I validated the change (though i had to tweak the comments so that the utf-8 encoding was within first 1024 bytes for https://validator.w3.org/ to accept it, another change for another day),,