SOP: Drop priority and changefreq

SOP: Drop priority and changefreq

<priority> and <changefreq> are ignored by Google — and bloat the file. Clean them out:

— ✅ Remove every <priority> tag (Google has confirmed it's unused)
— ✅ Remove every <changefreq> tag (also unused as a crawl signal)
— ✅ Keep only <loc> and an accurate <lastmod>
— ✅ Resulting file is smaller → faster fetch, more headroom under 50 MB

Why bother removing, not just ignoring: on a 50k-URL file these two tags add ~3-5 MB of dead weight that pushes long-URL sitemaps toward the 50 MB ceiling.

A minimal valid entry is two lines: <loc> and <lastmod>.

Definition of done: grep -c priority sitemap.xml returns 0, and the file shrank.