metainfo: move away from deprecated appdata

rpcs3/CMakeLists.txt

@@ -165,7 +165,7 @@ if(UNIX AND NOT APPLE)
         DESTINATION ${CMAKE_INSTALL_PREFIX}/share/icons/hicolor/48x48/apps)
     install(FILES rpcs3.desktop
         DESTINATION ${CMAKE_INSTALL_PREFIX}/share/applications)
-    install(FILES rpcs3.appdata.xml
+    install(FILES rpcs3.metainfo.xml
             DESTINATION ${CMAKE_INSTALL_PREFIX}/share/metainfo)
     # Install other files
     install(DIRECTORY ../bin/Icons