Fixing copy and paste bug/typo

As mentioned in the original project [related bug](agnoster#9 (comment)), the `bits` variable would never be reached because the `skip` one cannot possibly be less than zero.

I am not sure this solves anyhow possible library gotchas, but for sure it removes a condition brought there by a copy and paste, and able to make every linter complain about `bits` being undefined.

lib/base32.js

@@ -138,7 +138,7 @@ function Decoder() {
     }
 
     this.finish = function(check) {
-        var output = this.output + (skip < 0 ? alphabet[bits >> 3] : '') + (check ? '$' : '')
+        var output = this.output + (check ? '$' : '')
         this.output = ''
         return output
     }