libdpkg: Do not unnecessarily shut up stdout in t-subproc

The only problematic output comes from stderr.

debian/changelog

@@ -74,6 +74,8 @@ dpkg (1.17.7) UNRELEASED; urgency=low
   * Require compound literals support in the compiler at configure time.
   * Fix compound literals usage with compilers in C99 mode, by not assigning
     them to static variables.
+  * Test suite cleanup:
+    - Do not unnecessarily shut up stdout in t-subproc.
 
   [ Updated dpkg translations ]
   * German (Sven Joachim).

lib/dpkg/test/t-subproc.c

@@ -81,10 +81,9 @@ test(void)
 {
 	int fd;
 
-	/* XXX: Shut up output, we just want the error code. */
+	/* XXX: Shut up stderr, we don't want the error output. */
 	fd = open("/dev/null", O_RDWR);
 	test_pass(fd >= 0);
-	dup2(fd, 1);
 	dup2(fd, 2);
 
 	test_subproc_fork();