build: drop non-deterministic lastBuildDate from RSS feed

Remove the new Date() lastBuildDate from the generated feed so the RSS
output is reproducible across builds (matches the static-export goal of
deterministic artifacts).

Author: rudra-iitm

public/feed.xml

@@ -5,7 +5,6 @@
     <link>https://openprinting.github.io/</link>
     <description>Latest news and updates from the OpenPrinting project</description>
     <language>en-us</language>
-    <lastBuildDate>Sun, 07 Jun 2026 07:34:43 GMT</lastBuildDate>
     <atom:link href="https://openprinting.github.io/feed.xml" rel="self" type="application/rss+xml" />
     <item>
       <title>libcups v3.0.2</title>

scripts/generate-rss.ts

@@ -87,7 +87,6 @@ async function generateRss() {
     <link>${SITE_URL}/</link>
     <description>${escapeXml(SITE_DESCRIPTION)}</description>
     <language>en-us</language>
-    <lastBuildDate>${new Date().toUTCString()}</lastBuildDate>
     <atom:link href="${SITE_URL}${siteConfig.urls.rssPath}" rel="self" type="application/rss+xml" />
 ${items}
   </channel>