Shelve matrix for now

In tests it's too unreliable and appears not to work with standard browsers

src/freedombone-app-matrix

 VARIANTS='full full-vim chat'
 
 IN_DEFAULT_INSTALL=0
-SHOW_ON_ABOUT=1
+SHOW_ON_ABOUT=0
 
 MATRIX_DATA_DIR='/var/lib/matrix'
 MATRIX_HTTP_PORT=8558