Revert "os: Try to discover the current seat with the XDG_SEAT var first"

This reverts commit b27eaa7283.

os/utils.c

@@ -681,7 +681,6 @@ ProcessCommandLine(int argc, char *argv[])
                     ErrorF("Failed to disable listen for %s transport",
                            defaultNoListenList[i]);
     }
-    SeatId = getenv("XDG_SEAT");
 
     for (i = 1; i < argc; i++) {
         /* call ddx first, so it can peek/override if it wants */