Temporarily :-) fix typo in fake.gen_inventory.sh

I can't help it and everyone knows it too. Even a typo in a temporary
file is a terrible tragedy that must be fixed. It has to be done. It
cannot be ignored! You might just want to call me the IOCCC corrections
officer! :-)

tmp/fake.gen_inventory.sh

@@ -59,7 +59,7 @@ Exit codes:
      0	    all OK
      2	    -h and help string printed or -V and version string printed
      3	    command line error
-     4	    cannot find writiable winner directory
+     4	    cannot find writable winner directory
  >= 10	    internal error
 
 $NAME version: $VERSION"