Change .aup3 MIMEtype to x-audacity-project

.aup3 isn't a Tenacity project file, it's just that Tenacity uses the
Audacity project file format.

Signed-off-by: Sol Fisher Romanoff <sol@solfisher.com>
Reference-to: https://github.com/tenacityteam/tenacity/pull/638

images/CMakeLists.txt

@@ -9,7 +9,7 @@ def_vars()
 # This isn't really a target...
 
 list( APPEND PIXMAPS
-   ${_SRCDIR}/gnome-mime-application-x-tenacity-project.xpm
+   ${_SRCDIR}/gnome-mime-application-x-audacity-project.xpm
    ${_SRCDIR}/icons/16x16/tenacity16.xpm
    ${_SRCDIR}/icons/32x32/tenacity32.xpm
    ${_SRCDIR}/icons/48x48/tenacity.xpm

src/CMakeLists.txt

@@ -1227,7 +1227,7 @@ else()
   set( MIMETYPES "" )
 
   list( APPEND MIMETYPES
-    application/x-tenacity-project
+    application/x-audacity-project
   )
 
   if(USE_FFMPEG)