* fix header regex

lib/Text/Dokuwiki/Regexps.pm

@@ -16,7 +16,7 @@ $regexps->{header} = qr/
   \s*               # leading spaces
   (?<header> .+? )  # header text
   $SP*              # trailing spaces
-  (?: \g{line}? )   # header mark (exactly same as above)
+  (?: \g{line} )    # header mark (exactly same as above)
   (?: $EOL | $)     # newline or file end
 )
 /mx;