dwm no longer puts firefox on 9

dwm is supposed to put Firefox windows on the ninth tab.

/* xprop(1):
* WM_CLASS(STRING) = instance, class
* WM_NAME(STRING) = title
*/
/* class instance title tags mask isfloating monitor */
{ "Firefox", NULL, NULL, 1 << 8, 0, -1 },

However, recent firefox versions report this in xprop:

WM_CLASS(STRING) = "Navigator", "firefox"

Now the firefox windows show up anywhere.

chrome shows up on tab 9 as expected.