Fix incorrect comment

This file has a lot of what-commenting, somewhat by necessity,
because regular expressions.

Mostly that's OK, but occasionally it diverges.

Found while tweeting https://twitter.com/izs/status/672857319739232256

Author: isaacs

semver.js

@@ -836,7 +836,7 @@ function replaceTilde(comp, loose) {
     else if (isX(m))
       ret = '>=' + M + '.0.0 <' + (+M + 1) + '.0.0';
     else if (isX(p))
-      // ~1.2 == >=1.2.0- <1.3.0-
+      // ~1.2 == >=1.2.0 <1.3.0
       ret = '>=' + M + '.' + m + '.0 <' + M + '.' + (+m + 1) + '.0';
     else if (pr) {
       debug('replaceTilde pr', pr);