manage: Make sure c->isfixed is applied before floating checks

Commit 8806b6e237 ("manage: propertynotify: Reduce cost of unused size
hints") mistakenly removed an early size hints update that's needed to
populate c->isfixed for floating checks at manage() time. This resulted
in fixed (size hint min dimensions == max dimensions) subset of windows
not floating when they should.

See https://lists.suckless.org/dev/2204/34730.html for discussion.

dwm.c

@@ -1061,6 +1061,7 @@ manage(Window w, XWindowAttributes *wa)
 	XSetWindowBorder(dpy, w, scheme[SchemeNorm][ColBorder].pixel);
 	configure(c); /* propagates border_width, if size doesn't change */
 	updatewindowtype(c);
+	updatesizehints(c);
 	updatewmhints(c);
 	XSelectInput(dpy, w, EnterWindowMask|FocusChangeMask|PropertyChangeMask|StructureNotifyMask);
 	grabbuttons(c, 0);