util-linux: fix style

Author: dduugg

Formula/u/util-linux.rb

@@ -138,7 +138,7 @@ def caveats
 
     flags = ["x", "w", "r"] * 3
     perms = flags.each_with_index.reduce("") do |sum, (flag, index)|
-      sum.insert 0, ((stat.mode & (2 ** index)).zero? ? "-" : flag)
+      sum.insert 0, (stat.mode.nobits?(2 ** index) ? "-" : flag)
     end
 
     out = shell_output("#{bin}/namei -lx /usr").split("\n").last.split