Remove more dead code from minzip.

I've added explanatory comments to mzExtractRecursive because
that function will live on as a utility even after we move the
zip format related logic to libziparchive.

bug: 19472796

(cherry-picked from commit c9ccdfd7a42de08c47ab771b94dc5b9d1f957b95)

Change-Id: I8b7fb6fa3eafb2e7ac080ef7a7eceb691b252d8a
diff --git a/updater/install.c b/updater/install.c
index 2b2ffb0..01a5dd2 100644
--- a/updater/install.c
+++ b/updater/install.c
@@ -496,7 +496,7 @@
     struct utimbuf timestamp = { 1217592000, 1217592000 };  // 8/1/2008 default
 
     bool success = mzExtractRecursive(za, zip_path, dest_path,
-                                      MZ_EXTRACT_FILES_ONLY, &timestamp,
+                                      &timestamp,
                                       NULL, NULL, sehandle);
     free(zip_path);
     free(dest_path);