dpkg: Move <dpkg/tarfn.h> inclusion from cleanup.c to archives.h

The former is not using any declarations from tarfn.h, but the latter
is.

src/archives.h

@@ -23,6 +23,8 @@
 
 #include <stdbool.h>
 
+#include <dpkg/tarfn.h>
+
 struct tarcontext {
   int backendpipe;
   struct pkginfo *pkg;

src/cleanup.c

@@ -37,7 +37,6 @@
 #include <dpkg/i18n.h>
 #include <dpkg/dpkg.h>
 #include <dpkg/dpkg-db.h>
-#include <dpkg/tarfn.h>
 #include <dpkg/myopt.h>
 
 #include "filesdb.h"