amtterm: fix broken homepage link

The previous homepage at kraxel.org/cgit/amtterm/ returns a 404. The
package source is already fetched from GitHub, so updated the homepage
to match.

pkgs/by-name/am/amtterm/package.nix

@@ -49,7 +49,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   meta = {
     description = "Intel AMT® SoL client + tools";
-    homepage = "https://www.kraxel.org/cgit/amtterm/";
+    homepage = "https://github.com/kraxel/amtterm";
     license = lib.licenses.gpl2Plus;
     platforms = lib.platforms.linux;
   };