Appdata: Fix update_contact to pass validation

Author: Foldex

data/io.github.Foldex.AdwSteamGtk.appdata.xml.in

@@ -2,7 +2,7 @@
 <component type="desktop">
   <metadata_license>CC0-1.0</metadata_license>
   <project_license>GPL-3.0-or-later</project_license>
-  <update_contact>foldex|at|pm|dot|me</update_contact>
+  <update_contact>foldex_at_pm.dot.me</update_contact>
 
   <content_rating type="oars-1.1" />