Fix broken stdlib links in regexes article

Turn them from relative to absolute
They were broken since articles are now hosted under /articles/

Author: oleobal

articles/regular-expression.dd

@@ -285,6 +285,6 @@ $(D_S $(TITLE),
 )
 Macros:
 DOLLAR = $
-STD = $(LINK2 phobos/std_$0.html, std.$0)
+STD = $(LINK2 /phobos/std_$0.html, std.$0)
 SUBNAV=$(SUBNAV_ARTICLES)
 TITLE=Regular Expressions