Remove dependence on jsdelivr.net and possible unneeded dependency on chartist.js

[kriswest]

Describe the bug
A couple of the web UI's dependencies are loaded via jsdelivr URLs, but could/should be loaded from the deployment instead (which will ensure that the version matches the dependency version, that dependency scanning tools can accurately report on it and that any filtering of jsdelivr.net does not interfere with loading the dependency).

1. diff2html:

• git-proxy/index.html

  Lines 51 to 55 in ecd6161

  	<link
  	rel="stylesheet"
  	type="text/css"
  	href="https://cdn.jsdelivr.net/npm/diff2html/bundles/css/diff2html.min.css"
  	/>

• git-proxy/package.json

  Line 97 in ecd6161

  "diff2html": "^3.4.52",

2. chartist

• https://github.com/finos/git-proxy/blob/ecd616139ec2826ea72ab01f732ac67c403fdda2/index.html#L36C5-L40C15
• No dependency in package.json - are we even using this?