[tz] Converting tz-how-to.html to HTML 5

On 10/3/20 3:49 PM, Tim Parenti wrote:

(the VALIDATE=':' is because my MacBook doesn't have nsgmls).

The VALIDATE stuff in Makefile is needed only because I hadn't bothered to convert tz-how-to.html to HTML 5 with validator.w3.org checking, like the other web pages. I installed the attached proposed patch to do that, removing the need for VALIDATE etc. This is for maintenance convenience; it doesn't change the content of that web page, or its appearance on my Firefox 81 browser.