Update comments to match new std.regex examples

Example was switched to matchAll and 'g' was removed but the comment got left in. Another comment about match wasn't switched to matchAll.

std/regex.d

@@ -14,11 +14,10 @@
   void main()
   {
       // Print out all possible dd/mm/yy(yy) dates found in user input.
-      // g - global: find all matches.
       auto r = regex(r"\b[0-9][0-9]?/[0-9][0-9]?/[0-9][0-9](?:[0-9][0-9])?\b");
       foreach(line; stdin.byLine)
       {
-        // Match returns a range that can be iterated
+        // matchAll() returns a range that can be iterated
         // to get all subsequent matches.
         foreach(c; matchAll(line, r))
             writeln(c.hit);