Remove HTML footers or figure out a way to make them useful

> [...]
> 2. I think we should remove the HTML "footers" to reduce diffs further in the future, or at least the "last updated date". Note that the date is based on the file modification time, not the HTML build date, so it's a fairly random date right now, anyhow. I'll take care of this (in a separate PR).
> [...]

Sounds good. Would you mind adding an issue tracker for this and tag me? I'm almost guaranteed to forget this note, otherwise. Thanks!

_Originally posted by @dnovillo in https://github.com/KhronosGroup/SPIRV-Docs/issues/11#issuecomment-5623800340_

The issue mentions generated HTML footers and a last-updated date based on file modification time, but no file or test. Start by locating the HTML generation or template entry point and tracing how that date is produced. Done means either removing the footer metadata or implementing a useful alternative after the intended option is agreed.

Written by the indexing model from the issue text.