Change flatpak screenshots

Author: JanisV

io.github.opennumismat.open-numismat.metainfo.xml

@@ -21,15 +21,15 @@
   <screenshots>
     <screenshot type="default">
       <caption>Main window</caption>
-      <image>https://opennumismat.github.io/images/screenMain.png</image>
+      <image>https://opennumismat.github.io/images/screenMain-linux.png</image>
     </screenshot>
     <screenshot>
       <caption>Edit dialog</caption>
-      <image>https://opennumismat.github.io/images/screenEdit.png</image>
+      <image>https://opennumismat.github.io/images/screenEdit-linux.png</image>
     </screenshot>
     <screenshot>
       <caption>Statistics chart</caption>
-      <image>https://opennumismat.github.io/images/screenStatistics4.png</image>
+      <image>https://opennumismat.github.io/images/screenStatistics-linux.png</image>
     </screenshot>
   </screenshots>
   <branding>