fix typo

Author: zerosum0x0

modules/exploits/windows/smb/ms17_010_eternalblue.rb

@@ -101,7 +101,7 @@ def exploit
         # we don't need this sleep, and need to find a way to remove it
         # problem is session_count won't increment until stage is complete :\
         secs = 0
-        while !session_created? and sec < 5
+        while !session_created? and secs < 5
           secs += 1
           sleep 1
         end