Rename to GNOME LaTeX: AppData: provide old *.deskop file name

To not loose reviews and ratings.

See:
https://blogs.gnome.org/hughsie/2017/07/05/using-a-reverse-style-application-ids-in-your-application/

data/org.gnome.gnome-latex.appdata.xml.in

@@ -53,6 +53,9 @@
   <suggests>
     <id>evince.desktop</id>
   </suggests>
+  <provides>
+    <id>org.gnome.latexila.desktop</id>
+  </provides>
   <url type="homepage">https://wiki.gnome.org/Apps/LaTeXila</url>
   <url type="donation">https://liberapay.com/LaTeXila/</url>
   <url type="bugtracker">https://bugzilla.gnome.org/browse.cgi?product=latexila</url>