Fix XML namespaces URI

[jeromeroucou]

In order to modernize the code, the URLs have been changed from http to https. But XML namespaces have been modify too. This type of URL must not be changed. If namespace change, validation of sitemap XML file failed with original XSD file.

You can see URI namespace into XSD files :

• sitemap.xsd
• siteindex.xsd
• sitemap-image.xsd
• sitemap-news.xsd
• sitemap-video.xsd

[jeromeroucou]

For information, I'm working on a PR that will soon be submitted for review.